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  • 1.
    Andersson, Mattias
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics . Linköping University, The Institute of Technology.
    Inganäs , Olle
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics . Linköping University, The Institute of Technology.
    From short to long - Optical and electrical transients in photovoltaic bulk heterojunctions of polyfluorene/fullerenes2009In: Chemical Physics Letters, ISSN 0009-2614, E-ISSN 1873-4448, Vol. 357, no 1-3, p. 120-123Article in journal (Refereed)
    Abstract [en]

    We combine results from transient optical absorption in a bulk heterojunction polymer donor/fullerene acceptor material, obtained in the optical range as well as in the THz range, with results from electrical transients after a short light pulse, to present a unified interpretation of the transport of charge after the very first act of photoinduced charge transfer. We find that the mobility of charges is initially very high, but dramatically reduced with time, to arrive at values three orders of magnitude lower. We show that this can be understood as a consequence of the transport of hot charges by hopping through the density of states, from higher to lower energies.

  • 2.
    Berggren, Magnus
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Applied Physics. Linköping University, The Institute of Technology.
    Bergman, Peder
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Fagerström, Jan
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, The Institute of Technology.
    Inganäs, Olle
    Linköping University, Department of Physics, Chemistry and Biology, Applied Physics. Linköping University, The Institute of Technology.
    Andersson, Mats
    Chalmers Tekniska Högskola.
    Weman, Helge
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Granström, Magnus
    Linköping University, Department of Physics, Chemistry and Biology, Applied Physics. Linköping University, The Institute of Technology.
    Stafström, Sven
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, The Institute of Technology.
    Wennerström, O
    Chalmers Tekniska Högskola.
    Hjertberg, T
    Chalmers Tekniska Högskola.
    Controlling inter-chain and intra-chain excitations of a poly(thiophene) derivative in thin films1999In: Chemical Physics Letters, ISSN 0009-2614, E-ISSN 1873-4448, Vol. 304, no 1-2, p. 84-90Article in journal (Refereed)
    Abstract [en]

    The decay of photoexcitations in polythiophene chains has been studied in solid solutions of the polymer from room temperature to 4 K. A strong blue shift of the emission spectrum is observed in the polymer blend, as compared to the homopolymer. Dispersion of the polythiophene suppresses the non-radiative processes, which are suggested to be correlated to close contacts of polymer chains. Quantum chemistry modeling of the excited state distributed on two chains corroborate this conclusion.

  • 3. Biglino, D.
    et al.
    Bonora, M.
    Volodin, A.
    Boreskov Institute of Catalysis, 630090 Novosibirsk, Russian Federation.
    Lund, Anders
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Chemical Physics .
    Pulsed EPR study of the (NO)2-Na+ triplet state adsorption complex2001In: Chemical Physics Letters, ISSN 0009-2614, E-ISSN 1873-4448, Vol. 349, no 5-6, p. 511-516Article in journal (Refereed)
    Abstract [en]

    The (NO)2-Na+ triplet state complex stabilised in Na-A zeolites at low temperature was studied by pulsed EPR. The 3-pulse ESEEM spectra at 5 K were analysed by simulations in the time-domain, followed by Fourier transformation. The ESEEM was attributed to the interaction with Na+. The hyperfine coupling A(23Na)=(4.6, 4.6, 8.2) MHz and nuclear quadrupole Q(23Na)=(0.3, 0,3, -0.6) MHz tensors are of comparable magnitude as in the NO-Na+ complex determined earlier. The complexes are proposed to be either pairs of NO-Na+ or ON-Na+-NO.

  • 4. Birgerson, J.
    et al.
    Keil, M.
    Luo, Y.
    Theoretical Chemistry, Royal Institute of Technology, S-100 44 Stockholm, Sweden.
    Svensson, S.
    Department of Physics, Uppsala University, S-751 21 Uppsala, Sweden.
    Agren, H.
    Ågren, H., Theoretical Chemistry, Royal Institute of Technology, S-100 44 Stockholm, Sweden.
    Salaneck, William R
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry .
    A study of the electronic structure of ethylenedioxythiophene in gas phase using NEXAFS and quantum chemical calculations2004In: Chemical Physics Letters, ISSN 0009-2614, E-ISSN 1873-4448, Vol. 392, no 1-3, p. 100-104Article in journal (Refereed)
    Abstract [en]

    Near-edge X-ray absorption fine structure spectroscopy spectra of ethylenedioxythiophene has been recorded in gas phase at the carbon K-edge, sulphur L-edge and oxygen, K-edge. The experimental data has been interpreted with the help of a modified density functional code deMon. The good agreement between the calculated spectra and the measured one allows us to assign all observed resonances. The existence of p* resonances in both the measured and the calculated OK-edge adsorption spectrum demonstrate that the delocalized p-system of the thiophene part of the molecule is extended up to the oxygen atoms of the molecule. © 2004 Elsevier B.V. All rights reserved.

  • 5.
    Braun, Slawomir
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry . Linköping University, The Institute of Technology.
    Salaneck, William R.
    Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry . Linköping University, The Institute of Technology.
    Fermi level pinning at interfaces with tetrafluorotetracyanoquinodimethane (F4-TCNQ): The role of integer charge transfer states2007In: Chemical Physics Letters, ISSN 0009-2614, E-ISSN 1873-4448, Vol. 438, no 4-6, p. 259-262Article in journal (Refereed)
    Abstract [en]

    The energy level alignment of vacuum deposited molecular films of tetrafluorotetracyanoquinodimethane (F4-TCNQ) on various substrates has been studied by photoelectron spectroscopy. The interfaces studied span the work function range from 3.45 to 5.8 eV. In this range, the Fermi level of the substrate is pinned in proximity to LUMO level. This indicates that a charge transfer mechanism is responsible for the observed alignment scheme. The photoelectron emission study of sub-monolayer of F4-TCNQ revealed presence of electrons in the charge transfer states at the interface. In this context the electronic structure of neutral and negatively charged F4-TCNQ has been studied theoretically and by photoelectron spectroscopy.

  • 6.
    Buc, D.
    et al.
    Slovak University of Technology.
    Stuchlikova, L.
    Slovak University of Technology.
    Helmersson, Ulf
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Plasma and Coating Physics .
    Chang, W.H.
    University of Western Ontario.
    Bello, I.
    City University of Hong Kong.
    Investigation of RuO2/4H-SiC Schottky diode contacts by deep level transient spectroscopy2006In: Chemical Physics Letters, ISSN 0009-2614, E-ISSN 1873-4448, Vol. 429, no 4-6, p. 617-621Article in journal (Refereed)
    Abstract [en]

    Schottky diodes were prepared on n-type silicon carbide (4H-SiC) substrates by deposition of ruthenium dioxide contacts. Their electrical and electronic properties were investigated by current-voltage (I-V) and capacitance-voltage (C-V) methods, and deep level transient spectroscopy (DLTS). Five deep energy levels with thermal activation energies of approximately 0.27, 0.45, 0.56, 0.58 and 0.85 eV referenced to the conduction band minimum were revealed. The two energy levels at 0.56 and 0.85 eV are presumably induced by divacancies and the incorporation of ruthenium impurities into the SiC interfacial region. The Schottky diode structures are typical with a barrier height of 0.88 eV, and the I-V characteristics signify a saturation current of 10 pA with an ideality factor of 1.28.

  • 7.
    Carlegrim, Elin
    et al.
    Linköping University, Department of Science and Technology. Linköping University, The Institute of Technology.
    Kanciurzewska, Anna
    Linköping University, Department of Science and Technology. Linköping University, The Institute of Technology.
    de Jong, Michel P
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Fahlman, Mats
    Linköping University, Department of Science and Technology. Linköping University, The Institute of Technology.
    The unoccupied electronic structure of the semi-conducting room temperature molecular magnet V(TCNE)22008In: Chemical Physics Letters, ISSN 0009-2614, E-ISSN 1873-4448, Vol. 452, no 1-3, p. 173-177Article in journal (Refereed)
    Abstract [en]

    The unoccupied electronic structure of the organic-based magnet V(TCNE)x (TCNE = tetracyanoethylene, x~2) has been studied with near edge x-ray absorption fine structure (NEXAFS) and with photoelectron spectroscopy (PES). By studying V(TCNE)x upon sodium-doping, the electron-accepting state, i.e. the lowest unoccupied molecular orbital (LUMO) of V(TCNE)x was shown mainly to be localized on (TCNE)--units in contrast to the hole-accepting state, i.e. the highest occupied molecular orbital (HOMO), which previously was assigned primarily to be V(3d)-derived. This study also showed that there are trap states for electron transport located below the (TCNE)2- level, likely leading to decreased electron mobility.

  • 8.
    Cronstrand, P.
    et al.
    Theoretical Chemistry, Royal Institute of Technology, SCFAB, SE-106 91 Stockholm, Sweden.
    Luo, Y.
    Theoretical Chemistry, Royal Institute of Technology, SCFAB, SE-106 91 Stockholm, Sweden.
    Norman, Patrick
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Computational Physics .
    Agren, H.
    Ågren, H., Theoretical Chemistry, Royal Institute of Technology, SCFAB, SE-106 91 Stockholm, Sweden.
    Ab initio calculations of three-photon absorption2003In: Chemical Physics Letters, ISSN 0009-2614, E-ISSN 1873-4448, Vol. 375, no 1-2, p. 233-239Article in journal (Refereed)
    Abstract [en]

    We present large scale ab initio calculations of three-photon absorption of a series of dithienothiophene based charge transfer molecules using response theory within the random phase approximation. The structure-to-property relations obtained for the three-photon absorption cross-sections are discussed and compared with those for one- and two-photon absorption. © 2003 Published by Elsevier Science B.V.

  • 9.
    Durbeej, Bo
    et al.
    Uppsala University, Sweden and University of Sydney, Australia.
    Borg, O. Anders
    Uppsala University, Sweden.
    Eriksson, Leif A
    Örebro University, Sweden.
    Computational evidence in favor of a protonated chromophore in the photoactivation of phytochrome2005In: Chemical Physics Letters, ISSN 0009-2614, E-ISSN 1873-4448, Vol. 416, no 1-3, p. 83-88Article in journal (Refereed)
    Abstract [en]

    The photoactivation of the plant photoreceptor phytochrome is governed by a red-light-induced C15-Z  C15-E isomerization of the tetrapyrrolic chromophore phytochromobilin. From the viewpoint of experimental studies, ambiguity prevails as to whether the photoactivation involves a proton transfer from the chromophore to the surrounding protein. Here, we report a theoretical study addressing the effect of phytochromobilin protonation state on its photoisomerization by means of quantum chemical calculations. It is found that neutral forms of the chromophore are much less likely to photoisomerize than the parent, protonated form − a finding which supports the view that phytochromobilin remains protonated during phytochrome photoactivation.

  • 10.
    Durbeej, Bo
    et al.
    Uppsala University, Sweden.
    Eriksson, Leif A.
    Uppsala University, Sweden.
    On the bathochromic shift of the absorption by astaxanthin in crustacyanin: a quantum chemical study2003In: Chemical Physics Letters, ISSN 0009-2614, E-ISSN 1873-4448, Vol. 375, no 1-2, p. 30-38Article in journal (Refereed)
    Abstract [en]

    The structural origin of the bathochromic shift assumed by the electronic absorption spectrum of protein-bound astaxanthin, the carotenoid that upon binding to crustacyanin is responsible for the blue colouration of lobster shell, is investigated by means of quantum chemical methods. The calculations suggest that the bathochromic shift is largely due to one of the astaxanthin C4 keto groups being hydrogen-bonded to a histidine residue of the surrounding protein, and that the effect of this histidine is directly dependent on its protonation state. Out of the different methodologies (CIS, TD-DFT, and ZINDO/S) employed to calculate wavelengths of maximum absorption, the best agreement with experimental data is obtained using the semiempirical ZINDO/S method.

  • 11.
    Engstrom, Maria
    et al.
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Himo, F
    Linkoping Univ, Inst Phys & Measurement Technol, SE-58183 Linkoping, Sweden Univ Stockholm, Dept Phys, SE-11385 Stockholm, Sweden Royal Inst Technol, SE-10044 Stockholm, Sweden.
    Agren, H
    Linkoping Univ, Inst Phys & Measurement Technol, SE-58183 Linkoping, Sweden Univ Stockholm, Dept Phys, SE-11385 Stockholm, Sweden Royal Inst Technol, SE-10044 Stockholm, Sweden.
    Ab initio g-tensor calculations of the thioether substituted tyrosyl radical in galactose oxidase2000In: Chemical Physics Letters, ISSN 0009-2614, E-ISSN 1873-4448, Vol. 319, no 3-4, p. 191-196Article in journal (Refereed)
    Abstract [en]

    The tyrosyl radical in galactose oxidase is covalently cross-linked to a neighboring cysteine residue through a thioether bond. The role of this sulfur cross-link has been discussed ever since the crystal structure of the enzyme was solved. In the present work, the ab initio multiconfigurational linear response method is applied to calculate the g-tensor of unsubstituted and thioether substituted phenoxyl radicals. In contrast to some previous interpretations, but in agreement with recent EPR measurements, we find that the sulfur substitution induces only minor shifts in the g-tensor components. The spin distribution retains the odd-alternant pattern of the unsubstituted radical and only a small amount of spin is localized to the sulfur center. (C) 2000 Elsevier Science B.V. All rights reserved.

  • 12.
    Engstrom, Maria
    et al.
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Owenius, Rikard
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology.
    Vahtras, O.
    PDC, Roy. Inst. of Technology, SE-100 44, Stockholm, Sweden.
    Ab initio g-tensor calculations of hydrogen bond effects on a nitroxide spin label2001In: Chemical Physics Letters, ISSN 0009-2614, E-ISSN 1873-4448, Vol. 338, no 4-6, p. 407-413Article in journal (Refereed)
    Abstract [en]

    Hydrogen bonding effects on the electron paramagnetic resonance (EPR) g-tensor of a nitroxide spin label was investigated by quantum chemical calculations. The restricted open-shell Hartree-Fock (ROHF) linear response method with the atomic mean field approximation (AMFI) was used in the calculations. The results show that hydrogen bonding reduces the g-tensor component directed along the NO bond, gxx. This decrease is traced to higher excitation energy and lower spin-orbit coupling and angular momentum matrix elements for the n-p* excitation. The calculations show that the g-tensor is practically invariable when hydrogen bonding was modeled with methanol instead of water. © 2001 Elsevier Science B.V.

  • 13.
    Engstrom, Maria
    et al.
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Vahtras, O
    Linkoping Univ, Inst Phys & Measurement Technol, SE-58183 Linkoping, Sweden Royal Inst Technol, PDC, SE-10044 Stockholm, Sweden.
    Agren, H
    Linkoping Univ, Inst Phys & Measurement Technol, SE-58183 Linkoping, Sweden Royal Inst Technol, PDC, SE-10044 Stockholm, Sweden.
    MCSCF and DFT calculations of EPR parameters of sulfur centered radicals2000In: Chemical Physics Letters, ISSN 0009-2614, E-ISSN 1873-4448, Vol. 328, no 4-6, p. 483-491Article in journal (Refereed)
    Abstract [en]

    The EPR parameters of sulfur centered radicals are different depending on the radical structure, charge and solvent. That is, the g- and A-tensor components provide significant patterns which may distinguish sulfur radical structures from each other. In the present work, these EPR parameters were calculated for monosulfide radicals (RS'), disulfide radicals (RSS.), radical cations ((RSSR+)-S-.) and anions ((RSSR-)-S-.), with R = CH3, using the MCSCF linear response and DFT/B3LYP methods. Results were in agreement with experimental data for the cases when well-resolved EPR spectra are available. Especially, the assignment of the disulfide anion in ribonucleotide reductase was confirmed. The results indicate that investigations with the present computational methods on refined structures and solvent modeling may provide interpretations of experimental data on unassigned radical species. (C) 2000 Elsevier Science B.V. All rights reserved.

  • 14.
    Erdtman, Edvin
    et al.
    Institutionen för naturvetenskap and Modelling and Simulation Research Center, Örebro University, Sweden.
    dos Santos, Daniel J. V. A.
    i. Med. UL/Institute for Medicine and Pharmaceutical Sciences, Faculty of Pharmacy, University of Lisbon. Av. Prof. Gama Pinto, Lisbon, Portugal.
    Löfgren, Lennart
    Head- and Neck Oncology Center, Örebro University Hospital, Örebro, Sweden.
    Eriksson, Leif A.
    Örebro universitet, Institutionen för naturvetenskap.
    Modelling the behavior of 5-aminolevulinic acid and its alkyl esters in a lipid bilayer2008In: Chemical Physics Letters, ISSN 0009-2614, E-ISSN 1873-4448, Vol. 463, no 1-3, p. 178-182Article in journal (Refereed)
    Abstract [en]

    5-Aminolevulinic acid (5ALA) and ester derivates thereof are used as prodrugs in photodynamic therapy (PDT). The behavior of 5ALA and three esters of 5ALA in a DPPC lipid bilayer is investigated. In particular, the methyl ester displays a very different free energy profile, where the highest barrier is located in the region with highest lipid density, while the others have their peak in the middle of the membrane, and also displays a considerably lower permeability coefficient than neutral 5ALA and the ethyl ester. The zwitterion of 5ALA has the highest permeability constant, but a significant free energy minimum in the polar head-group region renders an accumulation in this region.

  • 15.
    Erdtman, Edvin
    et al.
    Örebro universitet, Institutionen för naturvetenskap.
    Eriksson, Leif A.
    Örebro universitet, Institutionen för naturvetenskap.
    Theoretical study of 5-aminolevulinic acid (5ALA) and some pharmaceutically important derivatives2007In: Chemical Physics Letters, ISSN 0009-2614, E-ISSN 1873-4448, Vol. 434, no 1-3, p. 101-106Article in journal (Refereed)
    Abstract [en]

    5-Aminolevulinic acid (5ALA) is the key synthetic building block in protoporphyrin IX (PpIX), the heme chromophore in mitochondria. The addition of extracorporeal 5ALA and its alkyl ester derivatives are in current clinical use in photodynamical diagnostics and photodynamic therapy of tumors and skin disorders. In the current study density functional theory calculations are performed on 5ALA and its methyl, ethyl, and hexyl esters, in order to explore the basic chemical properties of these species. It is concluded that even in aqueous media the zwitterionic form of 5ALA is less stable than the non-zwitterionic one, that the local environment (lipid vs water) affects the energetics of reaction considerably, and that the hexyl species is most prone to hydrolysis of the three alkyl ester derivatives.

  • 16.
    Fauquet, C.
    et al.
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Dannetun, Per
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Fredriksson, C.
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Stafström, Sven
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Bourée, J. E.
    CNRS, Laboratoire de Meudon, Meudon, France.
    Brillaud, P.
    SMI Organometallics Division, 13 000 Marseille, France.
    Bouanah, N.
    SMI Organometallics Division, 13 000 Marseille, France.
    Salaneck, William R.
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Electronic structure of trimethylamine alane in the solid state1995In: Chemical Physics Letters, ISSN 0009-2614, E-ISSN 1873-4448, Vol. 235, no 5-6, p. 528-534Article in journal (Refereed)
    Abstract [en]

    The chemical and electronic structure of ultrathin molecular films of trimethylamine alane (TMAA), condensed in UHV at − 100°C, have been studied in the solid state, using both X-ray and ultraviolet photoelectron spectroscopy. The results are analyzed with the help of quantum chemical calculations at the ab initio Hartree-Fock 6-31G∗ level. Based upon the good agreement between theory and experimental, it is determined that clean, oxygen-free, condensed molecular solid films consist of the 2:1 adduct of TMAA, which was previously uncertain. In addition, based upon the electronic structure results, it is clear that the mechanism of the photodecomposition of TMAA can be explained in terms of the wavefunction of electrons photoexcited into the first unoccupied molecular orbital.

  • 17.
    Ferreira Monteiro, Fabio
    et al.
    University of Brasilia, Brazil.
    Lima Azevedo, David
    University of Brasilia, Brazil; University of Brasilia, Brazil.
    Carlos da Silva, Eder
    University of Brasilia, Brazil.
    Ribeiro Jr., Luiz Antonio
    Linköping University, Department of Physics, Chemistry and Biology. University of Brasilia, Brazil; University of Brasilia, Brazil.
    Luciano de Almeida Fonseca, Antonio
    University of Brasilia, Brazil; University of Brasilia, Brazil.
    Encapsulated beta-carotene in ZnO nanotubes: Theoretical insight into the stabilization dynamics2015In: Chemical Physics Letters, ISSN 0009-2614, E-ISSN 1873-4448, Vol. 636, p. 62-66Article in journal (Refereed)
    Abstract [en]

    The stabilization dynamics of a molecular dye (beta-carotene) encapsulated in single-wall zinc oxide nanotubes (ZnONTs) is theoretically investigated in the scope of molecular dynamics and density functional theory simulations. Our findings show that the beta-carotene encapsulation in ZnONTs is an energetically favorable process. Once encapsulated, this molecular dye remains close to the ZnONT wall, in accordance with recent experimental reports. Interestingly, the interaction between the beta-carotene and ZnONT can form a charge delocalization state, where an amount of charge concentrated on beta-carotene is transferred to ZnONT. (C) 2015 Elsevier B.V. All rights reserved.

  • 18.
    Fionov, A.V.
    et al.
    Moscow MV Lomonosov State University.
    Lund, Anders
    Linköping University, Department of Physics, Chemistry and Biology, Chemical Physics . Linköping University, The Institute of Technology.
    Chen, Weimin
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Rozhkova, N.N.
    RAS.
    Buyanova, Irina
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Emelyanova, G.I.
    Moscow MV Lomonosov State University.
    Gorlenko, L.E.
    Moscow MV Lomonosov State University.
    Golubina, E.V.
    Moscow MV Lomonosov State University.
    Lokteva, E.S.
    Moscow MV Lomonosov State University.
    Osawa, E.
    Shinshu University.
    Lunin, V.V.
    Moscow MV Lomonosov State University.
    Paramagnetic centers in detonation nanodiamonds studied by CW and pulse EPR2010In: Chemical Physics Letters, ISSN 0009-2614, E-ISSN 1873-4448, Vol. 493, no 04-Jun, p. 319-322Article in journal (Refereed)
    Abstract [en]

    Dispersed detonation nanodiamonds have been studied by continuous-wave (CW) and pulse EPR techniques. The spectrum of bulk radicals (g = 2.0025 +/- 0.0002, a Lorentz line shape with Delta H-pp = 0.95 +/- 0.05 mT) dominated in CW EPR and prevented to record spectra from other paramagnetic species. The pulse EPR-spectrum was the superposition of the distorted P1-center spectrum with parameters (g = 2.0025, A(xx) = 2.57 mT, A(yy) = 3.08 mT, A(zz) = 4.07 mT), the H1-center spectrum (g = 2.0028) and the single line (g = 2.0025, DHpp = 0.40 +/- 0.05 mT) from other centers which may be assigned to surface radicals. The concentration of P1-centers has been estimated by CW EPR as 2 +/- 1 ppm N.

  • 19.
    Freitas, R R Q.
    et al.
    University of Federal Bahia, Brazil .
    Gueorguiev, Gueorgui Kostov
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    de Brito Mota, F
    University of Federal Bahia, Brazil .
    de Castilho, C M C.
    University of Federal Bahia, Brazil .
    Stafström, Sven
    Linköping University, Department of Physics, Chemistry and Biology, Computational Physics. Linköping University, The Institute of Technology.
    Kakanakova-Georgieva, Anelia
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Reactivity of adducts relevant to the deposition of hexagonal BN from first-principles calculations2013In: Chemical Physics Letters, ISSN 0009-2614, E-ISSN 1873-4448, Vol. 583, p. 119-124Article in journal (Refereed)
    Abstract [en]

    First-principles calculations, which also implement the nudged elastic band (NEB) code, are performed to investigate (i) the stability of the (C2H5)(3)B:NH3 adduct formed by the initial precursor molecules triethylborane (C2H5)(3)B and ammonia NH3 in the metal-chemical-vapor-deposition (MOCVD) of hexagonal BN, and (ii) the energy barrier to the first ethane elimination through consistent unimolecular, ammonia-assisted, and adduct-assisted reaction pathways. Comparison is done with the reference case of the (CH3)(3)Al:NH3 adduct, notoriously known for its high degree of stability and reactivity, which determines an overall severe parasitic gas-phase chemical reaction mechanism in the deposition of AlN.

  • 20.
    Friedlein, Rainer
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry .
    Crispin, Xavier
    Linköping University, The Institute of Technology. Linköping University, Department of Science and Technology.
    Pickholz, M.
    Keil, M.
    Stafström, Sven
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Computational Physics .
    Salaneck, William R
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry .
    High intercalation levels in lithium perylene stoichiometric compounds2002In: Chemical Physics Letters, ISSN 0009-2614, E-ISSN 1873-4448, Vol. 354, no 5-6, p. 389-394Article in journal (Refereed)
    Abstract [en]

    Both amorphous and polycrystalline films of the aromatic hydrocarbon perylene are found to accept as high as one lithium per 3.3±0.1 carbon atoms. Phases composed of stoichiometric compounds with two, four and six lithium atoms per molecule are observed. The intercalation involves a substantial charge transfer from the lithium atoms to the molecules. Moreover, a high binding energy of the dopant-induced valence band electronic states is observed by photoelectron spectroscopy. Those observations suggest a high energy storage capacity for small- and medium-size aromatic hydrocarbons and their potential use in batteries. © 2002 Elsevier Science B.V. All rights reserved.

  • 21.
    Grage, M.M.-L.
    et al.
    Department of Chemical Physics, Lund University, PO Box 124, S-221 00, Lund, Sweden.
    Pullerits, T.
    Department of Chemical Physics, Lund University, PO Box 124, S-221 00, Lund, Sweden.
    Ruseckas, A.
    Department of Chemical Physics, Lund University, PO Box 124, S-221 00, Lund, Sweden.
    Theander, M.
    Inganäs, Olle
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics .
    Sundstrom, V.
    Sundström, V., Department of Chemical Physics, Lund University, PO Box 124, S-221 00, Lund, Sweden.
    Conformational disorder of a substituted polythiophene in solution revealed by excitation transfer2001In: Chemical Physics Letters, ISSN 0009-2614, E-ISSN 1873-4448, Vol. 339, no 1-2, p. 96-102Article in journal (Refereed)
    Abstract [en]

    Anisotropy and isotropic transient absorption decays of a polythiophene derivative in dilute solution have been measured and compared to calculated decays on Monte Carlo simulated polymer chains to obtain knowledge about the geometrical conformation of the polymer. The polymer chain conformations are generated by a partially correlated self-avoiding random walk. Excitation migration along the isolated chain is modeled assuming a hopping mechanism. This approach can be used to determine conformational disorder and possible realizations of the polymer chains in solution as well as the trapping time and migration length of the excitation. © 2001 Elsevier Science B.V.

  • 22.
    Granlund, Thomas
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Applied Physics. Linköping University, The Institute of Technology.
    Theander, Mathias
    Linköping University, Department of Physics, Chemistry and Biology, Applied Physics. Linköping University, The Institute of Technology.
    Berggren, Magnus
    Linköping University, Department of Physics, Chemistry and Biology, Applied Physics. Linköping University, The Institute of Technology.
    Andersson, M
    Chalmers Tekniska Högskola.
    Ruzeckas, A
    Lunds universitet.
    Sundström, V
    Lunds universitet.
    Björk, G
    KTH.
    Granström, Magnus
    Linköping University, Department of Physics, Chemistry and Biology, Applied Physics. Linköping University, The Institute of Technology.
    Inganäs, Olle
    Linköping University, Department of Physics, Chemistry and Biology, Applied Physics. Linköping University, The Institute of Technology.
    A polythiophene microcavity laser1998In: Chemical Physics Letters, ISSN 0009-2614, E-ISSN 1873-4448, Vol. 288, no 5-6, p. 879-884Article in journal (Refereed)
    Abstract [en]

    We report photopumped lasing in a microcavity device with a polythiophene layer as the emitter. These microcavity devices are built by joining two polymer coated dielectric mirrors at elevated temperature. When photopumping the film, a lasing threshold is observed at 120 nJ/cm(2). Comparative studies with fast pump-probe spectroscopy of thin polythiophene films and the same polymer in photopumped lasing studies, indicate that the gain coefficient is 80 +/- 20 cm(-1), and that the exciton concentration is 2 X 10(17) cm(-3) at the lasing transition, well below the exciton-exciton recombination level. (C) 1998 Elsevier Science B.V. All rights reserved.

  • 23.
    Greczynski, G
    et al.
    Linkoping Univ, Dept Phys, S-58183 Linkoping, Sweden.
    Fahlman, Mats
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry .
    Salaneck, William R
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry .
    Electronic structure of hybrid interfaces of poly(9,9-dioctylfluorene)2000In: Chemical Physics Letters, ISSN 0009-2614, E-ISSN 1873-4448, Vol. 321, no 5-6, p. 379-384Article in journal (Refereed)
    Abstract [en]

    In this Letter we report the results of a study of the energy level alignment at interfaces between ultra-thin films of poly(9,9-dioctylfluorene) and AlxOy SiO2 or gold substrates, prepared under ambient (air) conditions. In all the cases, vacuum level alignment occurs, and the work function tracks that of the substrates. There is no evidence of band bending in the pristine polymer layers up to 1100 Angstrom in film thickness. Upon increasing the electrical conductivity of the polymer films by continuous doping with sodium under ultra-high-vacuum conditions, the energy levels of the polymer film gradually shift towards higher binding energies and finally become substrate independent. (C) 2000 Elsevier Science B.V. All rights reserved.

  • 24.
    Gueorguiev, G.K.
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Neidhardt, Jörg
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Stafström, Sven
    Linköping University, Department of Physics, Chemistry and Biology, Computational Physics . Linköping University, The Institute of Technology.
    Hultman, Lars
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    First-principles calculations on the role of CN precursors for the formation of fullerene-like carbon nitride2005In: Chemical Physics Letters, ISSN 0009-2614, E-ISSN 1873-4448, Vol. 401, no 1-3, p. 288-295Article in journal (Refereed)
    Abstract [en]

    First-principles calculations were utilized to study the formation mechanisms of the fullerene-like structure in carbon nitride compounds in the context of aligned incorporation of CN precursors along edges of evolving sheets during vapor phase synthesis. The incorporation of CN dimers and cyanogen molecules promotes an initial stabilization of pentagon defects, necessary for the observed bending of graphene multilayers in these compounds. The theoretical results corroborate recent experimental findings suggesting that preformed CxNy species, besides C and N atoms and ions, play an important role during the growth of FL CNx thin films by reactive magnetron sputtering. © 2004 Elsevier B.V. All rights reserved.

  • 25.
    Gueorguiev, Gueorgui Kostov
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Furlan, Andrej
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Högberg, Hans
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Stafström, Sven
    Linköping University, Department of Physics, Chemistry and Biology, Computational Physics . Linköping University, The Institute of Technology.
    Hultman, Lars
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    First–principles calculations on the structural evolution of solid fullerene–like CPx2006In: Chemical Physics Letters, ISSN 0009-2614, E-ISSN 1873-4448, Vol. 426, no 4-6, p. 374-379Article in journal (Refereed)
    Abstract [en]

    The formation and structural evolution of fullerene-like (FL) carbon phosphide (CPx) during synthetic growth were studied by first-principles calculations. Geometry optimizations and comparison between the cohesive energies suggest stability for solid FL-CPx compounds. In comparison with fullerene-like carbon nitride, higher curvature of the graphene sheets and higher density of cross-linkages between them is predicted and explained by the different electronic properties of P and N. Cage-like and onion-like structures, both containing tetragons, are found to be typical for fullerene-like CPx. Segregation of P is predicted at fractions exceeding ~20 at.%.

  • 26.
    Gueorguiev, Gueorgui Kostov
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Computational Physics .
    Neidhardt, Jörg
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics.
    Stafström, Sven
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Computational Physics .
    Hultman, Lars
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics.
    First-principles calculations on the curvature evolution and cross-linkage in carbon nitride2005In: Chemical Physics Letters, ISSN 0009-2614, E-ISSN 1873-4448, Vol. 410, no 4-6, p. 228-234Article in journal (Refereed)
    Abstract [en]

    First-principles calculations were utilized to study the formation mechanisms and structural features of fullerene-like carbon nitride (FL CN x). Cohesive energy comparisons reveal the energy cost for different defects arising from substitution of C for N as a function of the nitrogen concentration. In FL CNx, combinations of pentagons and heptagons compete in causing graphene sheet curvature during the addition of CN-precursors and single species. Also, cross-linkage between graphene layers in FL CNx can be explained by the bond rotation due to incorporated N atoms. The computational results agree with recent experimental observations from the growth of FL CNx thin films. © 2005 Elsevier B.V. All rights reserved.

  • 27.
    Gueorguiev, Gueorgui Kostov
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics.
    Stafström, Sven
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Computational Physics .
    Hultman, Lars
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics.
    Nano-wire formation by self-assembly of silicon-metal cage-like molecules2008In: Chemical Physics Letters, ISSN 0009-2614, E-ISSN 1873-4448, Vol. 458, no 1-3, p. 170-174Article in journal (Refereed)
    Abstract [en]

    By using DFT calculations we show that nano-wires consisting of endohedral MSi12 cage-like molecules are stable especially for light transition metal elements (M = Fe, Ni, Co, Ti, V, and Cu). The nano-wire assemblies are stabilized by the metal atoms located along their principal axes and can be seen as close Si-based analogues of C nanotubes, but with hexagonal cross-section due to the D6h-symmetry of their MSi12 building blocks. Independently on M, with the increase in the length of a (MSi12)m nano-wire, its HOMO-LUMO gap decreases gradually. The metallic behavior of (MSi12)m defines them as possible conductive components for self-assembled nano-devices. © 2008 Elsevier B.V. All rights reserved.

  • 28.
    Hultell (Andersson), Magnus
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Computational Physics . Linköping University, The Institute of Technology.
    Stafström, Sven
    Linköping University, Department of Physics, Chemistry and Biology, Computational Physics . Linköping University, The Institute of Technology.
    Polaron dynamics in highly ordered molecular crystals2006In: Chemical Physics Letters, ISSN 0009-2614, E-ISSN 1873-4448, Vol. 428, no 4-6, p. 446-450Article in journal (Refereed)
    Abstract [en]

    From a numerical solution of the time-dependent Schrödinger equation and the lattice equation of motion we obtain a microscopic picture of polaron transport in highly ordered molecular crystals in the presence of an external electric field. We have chosen the pentacene single crystal as a model system, but study the transport as a function of the intermolecular interaction strength, J. We observe a smooth transition from a nonadiabatic to an adiabatic polaronic drift process over the regime 20 < J < 120 meV. For intermolecular interaction strengths above 120 meV the polaron is no longer stable and the transport becomes band like.

  • 29.
    Hussain, Mushtaque
    et al.
    Linköping University, Department of Science and Technology. Linköping University, The Institute of Technology.
    Khan, Azam
    Linköping University, Department of Science and Technology. Linköping University, Faculty of Educational Sciences.
    Nur, Omer
    Linköping University, Department of Science and Technology, Physics and Electronics. Linköping University, The Institute of Technology.
    Willander, Magnus
    Linköping University, Department of Science and Technology, Physics and Electronics. Linköping University, The Institute of Technology.
    Broitman, Esteban
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    The effect of oxygen-plasma treatment on the mechanical andpiezoelectrical properties of ZnO nanorods2014In: Chemical Physics Letters, ISSN 0009-2614, E-ISSN 1873-4448, Vol. 608, p. 235-238Article in journal (Refereed)
    Abstract [en]

    We have studied the effect of oxygen plasma treatment on piezoelectric response and on the mechanical stability of ZnO nanorods synthesized on FTO by using ACG method. XRD and SEM techniques have shown highly dense and uniformly distributed nanorods. The piezoelectric properties and mechanical stability of as-grown and oxygen plasma treated samples were investigated by using nanoindentation technique. The comparison of load–displacement curves showed that the oxygen plasma treated samples are much stiffer and show higher generated piezo-voltage. This study demonstrates that the oxygenplasma treatment is a good option to fabricate reliable and efficient nanodevices for enhanced generation of piezoelectricity.

  • 30.
    Jakobsson, Fredrik L. E.
    et al.
    Linköping University, Department of Science and Technology. Linköping University, The Institute of Technology.
    Crispin, Xavier
    Linköping University, Department of Science and Technology. Linköping University, The Institute of Technology.
    Lindell, Linda
    Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry. Linköping University, The Institute of Technology.
    Kanciurzewska, Anna
    Linköping University, Department of Science and Technology. Linköping University, The Institute of Technology.
    Fahlman, Mats
    Linköping University, Department of Science and Technology. Linköping University, The Institute of Technology.
    Salaneck, William R.
    Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry. Linköping University, The Institute of Technology.
    Berggren, Magnus
    Linköping University, Department of Science and Technology. Linköping University, The Institute of Technology.
    Towards all-plastic flexible light emitting diodes2006In: Chemical Physics Letters, ISSN 0009-2614, E-ISSN 1873-4448, Vol. 433, no 1-3, p. 110-114Article in journal (Refereed)
    Abstract [en]

    All-plastic light emitting diodes require the design and fabrication of low work function plastic electrodes. Here, we show that the work function of poly(3,4-ethylenedioxythiophene)-polystyrenesulfonic acid (PEDOT-PSS) can be decreased from 4.8 eV to 3.9 eV by surface reaction with the strong electron-donor tetrakis(dimethylamino)ethylene (TDAE). The surface modification was characterized by photoelectron spectroscopy and optical spectroscopy. The low work function plastic electrode was used in a first prototype for all-plastic light emitting diodes.

  • 31. Jensen, J.A.D.
    et al.
    Pocwiardowski, P.
    Gdansk University of Technology, Faculty of Electron. Telecom./Info., Gdansk, Poland.
    Persson, Per
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics.
    Hultman, Lars
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics.
    Moller, P.
    Møller, P., Dept. of Manufacturing Engr./Mngt., The Technical University of Denmark, Kemitorvet b. 204, DK-2800 Kgs. Lyngby, Denmark.
    Acoustic streaming enhanced electrodeposition of nickel2003In: Chemical Physics Letters, ISSN 0009-2614, E-ISSN 1873-4448, Vol. 368, no 5-6, p. 732-737Article, review/survey (Refereed)
    Abstract [en]

    Electrochemical deposition of Ni from a Watts-type electrolyte under the influence of high frequency ultrasound at both high (250 W) and low (5-10 W) power sonication was investigated. An improvement in the material distribution of the deposited Ni in millimeter-sized groove-features on the cathode surface was observed. A theory based on mechanical interaction between organic additives adhering to the cathode surface and ultrasonically induced streaming-phenomena is presented here to account for the observed uniform filling behaviour. The present study further indicates a correlation between fringe-patterns on the surface of the deposit and near-boundary acoustic streaming. © 2003 Elsevier Science B.V. All rights reserved.

  • 32. Johansson, A
    et al.
    Stafström, Sven
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Computational Physics .
    Interactions between molecular wires and a gold surface2000In: Chemical Physics Letters, ISSN 0009-2614, E-ISSN 1873-4448, Vol. 322, no 5, p. 301-306Article in journal (Refereed)
    Abstract [en]

    The thiol group attaches strongly to gold surfaces and can thus be used as interconnects of molecular wires in nano electronics. A phenyl molecule attached to gold via a thiol group has been investigated by ab initio Hartree-Fock calculations in order to understand electronic transport through the sulfur-gold bridge. In our analysis of the coupling between gold and the molecule, we found that the electronic system of the gold substrate interacts directly with the conducting states of the molecule and thus forms an ohmic contact to the molecular wire. (C) 2000 Elsevier Science B.V. All rights reserved.

  • 33.
    Kakanakova-Georgieva, Anelia
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Gueorguiev, Gueorgui Kostov
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics.
    Stafström, Sven
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Computational Physics .
    Hultman, Lars
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics.
    Janzén, Erik
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    AlGaInN metal-organic-chemical-vapor-deposition gas-phase chemistry in hydrogen and nitrogen diluents: First-principles calculations2006In: Chemical Physics Letters, ISSN 0009-2614, E-ISSN 1873-4448, Vol. 431, no 4-6, p. 346-351Article in journal (Refereed)
    Abstract [en]

    Direct impact of H2 and N2 diluents on the metal-organic-chemical-vapor-deposition gas-phase chemistry in M(CH3)3/NH3 (M = Al, Ga, In) systems is identified in the framework of Density Functional Theory in terms of cohesive energy differences. While both diluents destabilize model reaction species, i.e. adducts, transition states and chain complexes, the effect is particularly strong with respect to N2 in the Al(CH3)3/NH3 system, and can be a factor to restrain the expansion of chain complexes that deplete the gas-phase from precursors. Theoretical results are supported by experimental evidences of higher growth rate and superior optical properties of AlN grown in N2 vs. H2 diluent. © 2006 Elsevier B.V. All rights reserved.

  • 34.
    Karazazi, Y.
    et al.
    Université de Mons-Hainaut.
    Crispin, Xavier
    Linköping University, The Institute of Technology. Linköping University, Department of Science and Technology.
    Kwon, O.
    Université de Mons-Hainaut.
    Bredas, J. L.
    Université de Mons-Hainaut.
    Cornil, J.
    Université de Mons-Hainaut.
    Influence of contact geometry and molecular derivatization on the interfacial interactions between gold and conjugated wires2004In: Chemical Physics Letters, ISSN 0009-2614, E-ISSN 1873-4448, Vol. 387, no 4-6, p. 502-508Article in journal (Refereed)
    Abstract [en]

    Self-assembled monolayers made of thiolated conjugated wires attached on gold surfaces currently attract a considerable interest in the field of nanoelectronics. The interactions taking place at the metal/molecule interface govern the electronic structure of the complex, and hence the barriers for charge injection from the electrodes to the molecules. Considering benzenethiol as a prototype molecule, we investigate here the way the electronic structure is affected by the nature of the anchoring site of the sulfur atom on the gold surface and by the relative orientation of the molecule with respect to the surface. We also assess whether the changes in the molecular electronic properties upon substitution are similar for the isolated molecule and for the molecule attached on the gold surface. Our results provide strong evidences that, in order to introduce functionalities and/or improve charge injection in molecular devices, the electronic properties of conjugated molecular wires can be tailored by derivatization independently of the metal electrodes. copy,

  • 35.
    Kashtanov, S.
    et al.
    Laboratory of Theoretical Chemistry, The Royal Institute of Technology, SCFAB, Stockholm SE-10691, Sweden.
    Rubio-Pons, O.
    Laboratory of Theoretical Chemistry, The Royal Institute of Technology, SCFAB, Stockholm SE-10691, Sweden.
    Luo, Y.
    Laboratory of Theoretical Chemistry, The Royal Institute of Technology, SCFAB, Stockholm SE-10691, Sweden.
    Agren, H.
    Ågren, H., Laboratory of Theoretical Chemistry, The Royal Institute of Technology, SCFAB, Stockholm SE-10691, Sweden.
    Stafström, Sven
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Computational Physics .
    Csillag, S.
    Department of Physics, Stockholm University, SCFAB, Stockholm SE-10691, Sweden.
    Characterization of aza-fullerene C58N2 isomers by X-ray spectroscopy2003In: Chemical Physics Letters, ISSN 0009-2614, E-ISSN 1873-4448, Vol. 371, no 1-2, p. 98-104Article in journal (Refereed)
    Abstract [en]

    X-ray photoelectron and near-edge X-ray absorption fine-structure spectra (NEXAFS) of four isomers of C58N2 are predicted by means of density-functional theory calculations. A strong isomer dependence for both types of spectra are found. The spectroscopic findings are discussed in conjunction with results from electronic and geometric structure optimizations. © 2003 Elsevier Science B.V. All rights reserved.

  • 36.
    Khan, Azam
    et al.
    Linköping University, Department of Science and Technology, Physics and Electronics. Linköping University, The Institute of Technology.
    Hussain, Mushtaque
    Linköping University, Department of Science and Technology. Linköping University, The Institute of Technology.
    Nur, Omer
    Linköping University, Department of Science and Technology, Physics and Electronics. Linköping University, The Institute of Technology.
    Willander, Magnus
    Linköping University, Department of Science and Technology, Physics and Electronics. Linköping University, The Institute of Technology.
    Fabrication of zinc oxide nanoneedles on conductive textile for harvesting piezoelectric potential2014In: Chemical Physics Letters, ISSN 0009-2614, E-ISSN 1873-4448, Vol. 612, p. 62-67Article in journal (Refereed)
    Abstract [en]

    Keeping the fact in mind that different morphologies have strong influence on piezoelectric properties, ZnO NNs were synthesized on textile for harvesting piezoelectricity. Piezoelectric potential was captured from ZnO NNs grown on textile by using AFM in contact mode. Structural study was carried out by using FESEM, HRTEM and XRD techniques. The recorded output potential and current was more than 45 mV and 150 nA. The combination of ZnO NNs and textile can be used effectively for energy harvesting applications and the use of textile fabric can pave the way for cheap, flexible, wearable, washable and environment friendly nanodevices.

  • 37.
    Koizumi, H.
    et al.
    Division of Molecular Chemistry, Grad. Sch. Eng., Hokkaido Univ., K., Sapporo, Japan.
    Takada, T.
    Division of Molecular Chemistry, Grad. Sch. Eng., Hokkaido Univ., K., Sapporo, Japan.
    Ichikawa, T.
    Division of Molecular Chemistry, Grad. Sch. Eng., Hokkaido Univ., K., Sapporo, Japan.
    Lund, Anders
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Chemical Physics .
    Photoinduced reactions of 1-(dimethylethyl)-2,2-dimethylpropyl and cyclohexyl radicals in low-temperature solids2001In: Chemical Physics Letters, ISSN 0009-2614, E-ISSN 1873-4448, Vol. 340, no 3-4, p. 256-260Article in journal (Refereed)
    Abstract [en]

    Photoinduced reactions of 1-(dimethylethyl)-2,2-dimethylpropyl and cyclohexyl radicals in 77 K solids were studied by the ESR method. 1-(Dimethylethyl)-2,2-dimethylpropyl is converted to 2,2,4,4-tetramethylpentyl radical with photoirradiation of 254 nm light. A hydrogen atom of methyl groups can hence directly transfer to the radical site at a carbon atom other than an adjacent one in the photoinduced reactions of alkyl radicals. Cyclohexyl radical is converted to cyclopentylmethyl radical with irradiation of 254 nm light. The photolysis of cyclohexyl radical causes C-C bond scission, and results in the formation of 5-hexenyl radical. It is then converted to cyclopentylmethyl radical through intramolecular rearrangement.

  • 38.
    Kostov Gueorguiev, Gueorgui
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Goyenola, Cecilia
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Schmidt, Susann
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Hultman, Lars
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    CF(x): A first-principles study of structural patterns arising during synthetic growth2011In: Chemical Physics Letters, ISSN 0009-2614, E-ISSN 1873-4448, Vol. 516, no 1-3, p. 62-67Article in journal (Refereed)
    Abstract [en]

    Structural and bonding patterns arising from the incorporation of fluorine atoms in a graphene-like network relevant to the deposition of carbon fluoride (CF(x)) films were addressed by first-principles calculations. We find that large N-member (N = 8-12) rings, defects by sheet branching, and defects associated with bond rotation pertain to CF(x). The cohesive energy gains associated with these patterns are similar to 0.2-0.4 eV/at., which is similar to those for a wide range of defects in other C-based nanostructured solids. Fullerene-like CF(x) is predicted for F concentrations below similar to 10 at.%, while CF(x) compounds with higher F content are predominantly amorphous or polymeric.

  • 39.
    Lenz, Annika
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Physical Chemistry . Linköping University, The Institute of Technology.
    Ojamäe, Lars
    Linköping University, Department of Physics, Chemistry and Biology, Physical Chemistry . Linköping University, The Institute of Technology.
    On the stability of dense versus cage-shaped water clusters: quantum-chemical investigations of zero-point energies, free energies, basis-set effects and IR spectra of (H2O)12 and (H2O)202006In: Chemical Physics Letters, ISSN 0009-2614, E-ISSN 1873-4448, Vol. 418, p. 361-367Article in journal (Refereed)
    Abstract [en]

    The energetics of water clusters with 12 and 20 molecules are studied by quantum-chemical computations using the B3LYP, MP2, MP4 and CCSD methods. The effect of electron-correlation method, basis set, zero-point energy, thermal energy and Gibbs free energy on the relative stability of fused clusters (structures consisting of cubic- or prismatic-shaped subparts) versus cage-shaped clusters (more open structures with only three-coordinated molecules) are investigated. The O–H stretching IR vibrational spectra are studied. The contribution of zero-point and Gibbs free energy will diminish the energy difference between fused- and cage-shaped clusters, but the fused structures are still slightly more favorable.

  • 40. Limal, E.R.A.
    et al.
    Boström, Mathias
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics .
    Sernelius, Bo
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics .
    Horinek, D.
    Netz, R.R.
    Biscaia, E.C.
    Kunz, W.
    Tavares, F.W.
    Forces between Air-Bubbles in Electrolyte Solution2008In: Chemical Physics Letters, ISSN 0009-2614, E-ISSN 1873-4448, Vol. 458, p. 299-302Article in journal (Refereed)
  • 41.
    Luo, Y.
    et al.
    Theoretical Chemistry, Roy. Inst. of Technology, S-10044, Stockholm, Sweden.
    Agren, H.
    Ågren, H., Theoretical Chemistry, Roy. Inst. of Technology, S-10044, Stockholm, Sweden.
    Keil, M.
    Friedlein, Rainer
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry .
    Salaneck, William R
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry .
    A theoretical investigation of the near-edge X-ray absorption spectrum of hexa- peri -hexabenzocoronene2001In: Chemical Physics Letters, ISSN 0009-2614, E-ISSN 1873-4448, Vol. 337, no 1-3, p. 176-180Article in journal (Refereed)
    Abstract [en]

    The near-edge X-ray absorption spectrum of hexa-peri-hexabenzocoronene has been simulated by density functional theory techniques using transition state and full core hole potentials. The total spectrum is found to be a composition of multiple structure in the subspectra of the symmetry unique carbons, rather than by chemically shifted single p* transitions. This quite 'fullerene-like' behavior, with only minor reminiscence of either graphite or benzene spectral features, is used to argue that long-range effects must be important to build up the dominating single excitonic p* feature in graphite. © 2001 Elsevier Science B.V.

  • 42.
    Malysheva, L.
    et al.
    Bogolyubov Inst. Theoretical Physics, Kiev 03143, Ukraine.
    Klymenko, Y.
    Space Research Institute, Kiev 03187, Ukraine.
    Onipko, A.
    Division of Physics, Luleå University of Technology, S-971 87 Luleå, Sweden.
    Valiokas, Ramunas
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology.
    Liedberg, Bo
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Sensor Science and Molecular Physics .
    Ab initio calculations of equilibrium geometries and vibrational excitations of helical ethylene-glycol oligomers: Application to modeling of monolayer infrared spectra2003In: Chemical Physics Letters, ISSN 0009-2614, E-ISSN 1873-4448, Vol. 370, no 3-4, p. 451-459Article in journal (Refereed)
    Abstract [en]

    The density functional theory methods are used to calculate the equilibrium molecular structures and vibrational spectra of helical H(CH2CH2O)nH (OEG) oligomers (n = 4-7) at a level of precision that has not been accomplished before. The largest deviation between experimentally observed frequencies, obtained from infrared reflection-absorption spectra of OEG-monolayers on gold, and calculated, single molecule frequencies (unscaled), is slightly above 2%. Moreover, the most intense peak in the CH2-stretching region at about 2890 cm-1, commonly regarded as a trademark of the OEG helical conformation, is reassigned in this study to the asymmetric CH2-stretching mode. © 2003 Elsevier Science B.V. All rights reserved.

  • 43. Nilsing, M
    et al.
    Persson, P
    Ojamäe, Lars
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Physical Chemistry .
    Anchor group influence on molecule-metal oxide interfaces: periodic hybrid DFT study of pyridine bound to TiO2 via carboxylic and phosphonic acid2005In: Chemical Physics Letters, ISSN 0009-2614, E-ISSN 1873-4448, Vol. 415, p. 375-380Article in journal (Refereed)
  • 44.
    Norman, Patrick
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Computational Physics. Linköping University, The Institute of Technology.
    Aa Jensen, Hans Jorgen
    University of So Denmark.
    Phosphorescence parameters for platinum (II) organometallic chromophores: A study at the non-collinear four-component Kohn-Sham level of theory2012In: Chemical Physics Letters, ISSN 0009-2614, E-ISSN 1873-4448, Vol. 531, p. 229-235Article in journal (Refereed)
    Abstract [en]

    A theoretical characterization of the phosphorescence decay traces of a prototypical platinum (II) organic chromophore has been conducted. The phosphorescence wavelength and radiative lifetime are predicted to equal 544 nm and 160 mu s, respectively. The third triplet state is assigned as participator in the inter-system crossing and is predicted to have a phosphorescence decay rate 12 times larger than that of the lowest triplet state. This result offers an explanation for the experimentally observed double exponential decay. The self-consistent field (SCF) optimization of the electron density was accomplished only after introducing algorithmic improvements, now incorporated in the DIRAC program.

  • 45. OJAMAE, LARS
    et al.
    HERMANSSON, KERSTI
    Uppsala universitet, Kemiska institutionen.
    PROBST, MICHAEL
    THE OH STRETCHING FREQUENCY IN LIQUID WATER SIMULATIONS - THE CLASSICAL ERROR1992In: Chemical Physics Letters, ISSN 0009-2614, E-ISSN 1873-4448, Vol. 191, no 5, p. 500-506Article in journal (Refereed)
    Abstract [en]

    OH stretching frequencies of HDO molecules in liquid water have been calculated by molecular dynamics simulation and compared to quantum-corrected OH stretching frequencies. In the MD simulation the MCY intermolecular water-water potential was used together with an experimental intramolecular free water potential. The frequencies calculated classically by Fourier transformation of the velocity autocorrelation function are found to be almost-equal-to 300 cm-1 too high compared with experiment. Quantum corrections show that the classical error contribution to this discrepancy is almost-equal-to 140 cm-1. To reach full agreement with experiment also the potential model needs to be improved. It is suggested that in constructing flexible water potentials the goal should not be set for an MD-derived OH frequency in absolute agreement with experiment (at 3400 cm-1) but instead some 200 cm-1 higher.

  • 46. OJAMAE, LARS
    et al.
    TEGENFELDT, JÖRGEN
    LINDGREN, JAN
    HERMANSSON, KERSTI
    Uppsala universitet, Kemiska institutionen.
    SIMULATION OF BAND WIDTHS IN LIQUID WATER SPECTRA - THE BREAKDOWN OF THE FROZEN-FIELD APPROXIMATION1992In: Chemical Physics Letters, ISSN 0009-2614, E-ISSN 1873-4448, Vol. 195, no 1, p. 97-103Article in journal (Refereed)
    Abstract [en]

    Band shapes of liquid water OH vibrational spectra oblained from molecular dynamics (MD) simulation and from a quantum-mechanical method are investigated. The so-called "frozen-field approximation" applied to the calculation of quantum-mechanical high-frequency vibrational spectra is critically examined. It is demonstrated that the band width of the OH stretching spectrum is seriously overestimated through the neglect of the dynamics of the environment in the frozen-field approximation. We show that the proper inclusion of the dynamics in this quantum-mechanical method leads not only to a correct absolute frequency for the model potential used, but also to the correct description of the band width. The basic steps in this method are: (1) an MD simulation yielding an ensemble of liquid water configurations, (2) a quantum-mechanical uncoupled local-mode calculation of the OH frequency for each molecule, using model potentials for the inter- and intra-molecular interactions, (3) inclusion of the influence from the dynamics of the surroundings by filtering out rapid frequency fluctuations. The remaining discrepancy between experimental and computed OH spectra is attributed to shortcomings in the potential model used.

  • 47.
    Osikowicz, Wojciech
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry .
    Murdey, R.
    Giles, M.
    Merck Chemicals, University Parkway, Southampton SO16 7QD, United Kingdom.
    Heeney, M.
    Merck Chemicals, University Parkway, Southampton SO16 7QD, United Kingdom.
    Tierney, S.
    Merck Chemicals, University Parkway, Southampton SO16 7QD, United Kingdom.
    McCulloch, I.
    Merck Chemicals, University Parkway, Southampton SO16 7QD, United Kingdom.
    Salaneck, William R
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry .
    Electronic structure of a novel alkylidene fluorene polymer in the pristine state2004In: Chemical Physics Letters, ISSN 0009-2614, E-ISSN 1873-4448, Vol. 385, no 3-4, p. 184-188Article in journal (Refereed)
    Abstract [en]

    The electronic structure of a novel conjugated polymer, polyalkylidene fluorene has been studied using a combined experimental-theoretical approach. The densities of states in the valence band region of the new derivative, poly(9-(1'-decylundecylidene)fluorene), were measured by ultraviolet photoelectron spectroscopy and compared with electronic band-structure calculations performed in the valence effective Hamiltonian framework. The results are compared with those of similar studies on the reference polymer poly(9,9-dioctylfluorene). We report the experimentally determined ionization potential for this new material and discuss the role of substitution in altering the electronic properties of the polymer backbone. © 2003 Elsevier B.V. All rights reserved.

  • 48.
    Persson, P.
    et al.
    Department of Quantum Chemistry, Uppsala University, P.O. Box 518, SE-751 20 Uppsala, Sweden.
    Lunell, S.
    Department of Quantum Chemistry, Uppsala University, P.O. Box 518, SE-751 20 Uppsala, Sweden.
    Ojamäe, Lars
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Physical Chemistry .
    Electronic interactions between aromatic adsorbates and metal oxide substrates calculated from first principles2002In: Chemical Physics Letters, ISSN 0009-2614, E-ISSN 1873-4448, Vol. 364, no 5-6, p. 469-474Article in journal (Refereed)
    Abstract [en]

    The electronic structure of interfaces between aromatic adsorbates and metal oxide surfaces has been investigated using periodic hybrid ab initio Hartree-Fock-density functional theory calculations. Strong interfacial electronic coupling is observed for isonicotinic acid adsorbed on ZnO(1 0 1¯ 0) and TiO2(1 1 0) surfaces. The results are in good agreement with experiments of ultrafast surface electron transfer processes for TiO2, and current experimental controversies regarding ZnO are clarified theoretically. © 2002 Elsevier Science B.V. All rights reserved.

  • 49.
    Persson, P
    et al.
    Uppsala universitet, Institutionen för kvantkemi.
    Ojamae, L
    Periodic Hartree-Fock study of the adsorption of formic acid on ZnO(10(1)over-bar-0)2000In: Chemical Physics Letters, ISSN 0009-2614, E-ISSN 1873-4448, Vol. 321, no 3-4, p. 302-308Article in journal (Refereed)
    Abstract [en]

    Adsorption of formic acid (HCOOH) on ZnO(10 (1) over bar 0) surfaces has been investigated by means of quantum-chemical ab initio periodic Hartree-Fock calculations. One 'bridging' structure, characterized by a formate anion symmetrically bonded via its t

  • 50.
    Ribeiro Junior, Luiz Antonio
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Chemistry. Linköping University, Faculty of Science & Engineering. University of Brasilia, Brazil; University of Brasilia, Brazil.
    Santiago de Brito, Sara
    University of Brasilia, Brazil.
    Henrique de Oliveira Neto, Pedro
    University of Brasilia, Brazil.
    Trap-assisted charge transport at conjugated polymer interfaces2016In: Chemical Physics Letters, ISSN 0009-2614, E-ISSN 1873-4448, Vol. 644, p. 121-126Article in journal (Refereed)
    Abstract [en]

    The trap-assisted charge transport in conjugated polymers is numerically investigated in the framework of a one-dimensional tight-binding model. Our findings show that a polaron trapped within an interchain region can be released migrating between the chains at low temperature regimes. Conversely, a trapped bipolaron cannot be released even considering high temperature values. Interestingly, for systems containing more than one polaron, the formation of trapped states is avoided and there is no charge transfer between the chains. Considering more than one bipolaron, the generation of trapped states occurs and a bipolaron can migrates between the chains. (C) 2015 Elsevier B.V. All rights reserved.

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