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Electronic and structural properties of nanoclusters
Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, Faculty of Science & Engineering.
2018 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Nanoclusters have gained a huge interest due to their unique properties. They represent an intermediate state between an atom and a solid, which manifests itself in their atomic configurations and electronic structure. The applications of nanoclusters require detailed understanding of their properties and strongly depend on the ability to control their synthesis process. Significant effort has been invested in modelling of nanoclusters properties. However, the complexity of these systems is such that many aspects of their growth process and properties are yet to be understood.

My thesis focuses on describing structural and electronic properties of nanoclusters. In particular, the model for nanoparticles growth in plasma condition is developed and applied, allowing to describe the influence of the plasma conditions on the evaporation, growth and morphological transformation processes. The mechanism driving the morphology transition from icosahedral to decahedral phase is suggested based on force-fields models. Spectroscopic methods allow for precise characterization of nanoclusters and constitute an important tool for analysis of their electronic structure of valence band as well as core-states. The special attention in the thesis is paid to the core-states of nanoclusters and influences that affect them. In particular, the effects of local coordination, interatomic distances and confinement effects are investigated in metal nanoclusters by density functional theory methods. These effects and their contribution to spectroscopic features of nanoclusters in X-ray photoemission are modelled. The relation between the reactivity of nanoclusters and their spectroscopic features calculated in different approximations are revealed and explained. Ceria is a very important system for many applications due to the ability of cerium atoms to change their oxidation state depending on the environment. The shift of the oxidation state and its effects on the core-states is examined with X-ray absorption measurements and modelling allowing to build a rigid foundation for interpretation of the measured spectra and characterization of electronic structure of ceria nanoparticles.  

Place, publisher, year, edition, pages
Linköping: Linköping University Electronic Press, 2018. , p. 78
Series
Linköping Studies in Science and Technology. Dissertations, ISSN 0345-7524 ; 1912
National Category
Theoretical Chemistry Other Physics Topics
Identifiers
URN: urn:nbn:se:liu:diva-145684DOI: 10.3384/diss.diva-145684ISBN: 9789176853498 (print)OAI: oai:DiVA.org:liu-145684DiVA, id: diva2:1190735
Public defence
2018-04-20, Planck, Fysikhuset, Campus Valla, Linköping, 10:15 (English)
Opponent
Supervisors
Available from: 2018-03-15 Created: 2018-03-15 Last updated: 2018-03-15Bibliographically approved
List of papers
1. Molecular dynamics simulation of the growth of Cu nanoclusters from Cu ions in a plasma
Open this publication in new window or tab >>Molecular dynamics simulation of the growth of Cu nanoclusters from Cu ions in a plasma
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2014 (English)In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 90, no 16, p. 165421-Article in journal (Refereed) Published
Abstract [en]

A recently developed method of nanoclusters growth in a pulsed plasma is studied by means of molecular dynamics. A model that allows one to consider high-energy charged particles in classical molecular dynamics is suggested, and applied for studies of single impact events in nanoclusters growth. In particular, we provide a comparative analysis of the well-studied inert gas aggregation method and the growth from ions in a plasma. The importance to consider of the angular distribution of incoming ions in the simulations of the nanocluster growth is underlined. A detailed study of the energy transfer from the incoming ions to a nanocluster, as well as the diffusion of incoming ions on the cluster surface, is carried out. Our results are important for understanding and control of the nanocluster growth process.

Place, publisher, year, edition, pages
American Physical Society, 2014
National Category
Physical Sciences
Identifiers
urn:nbn:se:liu:diva-112305 (URN)10.1103/PhysRevB.90.165421 (DOI)000343699900005 ()
Note

Funding Agencies|Knut and Alice Wallenberg Foundation [2012.0083]; Swedish Foundation for Strategic Research (SSF) [10-0026]; Russian Federation Ministry for Science and Education [14.Y26.31.0005]

Available from: 2014-11-24 Created: 2014-11-24 Last updated: 2018-03-15
2. Morphology transition mechanism from icosahedral to decahedral phase during growth of Cu nanoclusters
Open this publication in new window or tab >>Morphology transition mechanism from icosahedral to decahedral phase during growth of Cu nanoclusters
2015 (English)In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 92, no 2, p. 020102-Article in journal (Refereed) Published
Abstract [en]

The morphology transition from the thermodynamically favorable to the unfavorable phase during growth of freestanding copper nanoclusters is studied by molecular dynamics simulations. We give a detailed description of the kinetics and thermodynamics of the process. A universal mechanism of a solid-solid transition, from icosahedral to decahedral morphology in the nanoclusters, is proposed. We show that a formation of distorted NC during the growth process with islands of incoming atoms localized in certain parts of the grown particle may shift the energy balance between Ih and Dh phases in favor of the latter leading to the morphology transition deep within the thermodynamic stability field of the former. The role of diffusion in the morphology transition is revealed. In particular, it is shown that fast diffusion should suppress the morphology transition and favor homogeneous growth of the nanoclusters.

Place, publisher, year, edition, pages
American Physical Society, 2015
National Category
Physical Sciences
Identifiers
urn:nbn:se:liu:diva-120270 (URN)10.1103/PhysRevB.92.020102 (DOI)000357485400001 ()
Note

Funding Agencies|Knut and Alice Wallenberg Foundation [2012.0083]; Swedish Foundation for Strategic Research (SSF) program SRL Grant [10-0026]; Ministry of Education and Science of the Russian Federation [14.Y26.31.0005]

Available from: 2015-07-24 Created: 2015-07-24 Last updated: 2018-03-15
3. Nanoparticle growth by collection of ions: orbital motion limited theory and collision-enhanced collection
Open this publication in new window or tab >>Nanoparticle growth by collection of ions: orbital motion limited theory and collision-enhanced collection
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2016 (English)In: Journal of Physics D: Applied Physics, ISSN 0022-3727, E-ISSN 1361-6463, Vol. 49, no 39, p. 395208-Article in journal (Refereed) Published
Abstract [en]

The growth of nanoparticles in plasma is modeled for situations where the growth is mainly due to the collection of ions of the growth material. The model is based on the classical orbit motion limited (OML) theory with the addition of a collision-enhanced collection (CEC) of ions. The limits for this type of model are assessed with respect to three processes that are not included: evaporation of the growth material, electron field emission, and thermionic emission of electrons. It is found that both evaporation and thermionic emission can be disregarded below a temperature that depends on the nanoparticle material and on the plasma parameters; for copper in our high-density plasma this limit is about 1200 K. Electron field emission can be disregarded above a critical nanoparticle radius, in our case around 1.4 nm. The model is benchmarked, with good agreement, to the growth of copper nanoparticles from a radius of 5 nm-20 nm in a pulsed power hollow cathode discharge. Ion collection by collisions contributes with approximately 10% of the total current to particle growth, in spite of the fact that the collision mean free path is four orders of magnitude longer than the nanoparticle radius.

Place, publisher, year, edition, pages
IOP PUBLISHING LTD, 2016
Keywords
nanoparticle synthesis; pulsed plasma; complex plasmas
National Category
Fusion, Plasma and Space Physics
Identifiers
urn:nbn:se:liu:diva-132204 (URN)10.1088/0022-3727/49/39/395208 (DOI)000384239200004 ()
Note

Funding Agencies|Knut and Alice Wallenberg foundation [2014.0276]; Swedish Research Council under Linkoping Linneaus Environment LiLi-NFM [2008-6572]; Ministry of Education and Science of the Russian Federation [14.Y26.31.0005]; Increase Competitiveness Program of MISiS

Available from: 2016-11-01 Created: 2016-10-21 Last updated: 2018-03-15
4. Origin of the core-level binding energy shifts in Au nanoclusters
Open this publication in new window or tab >>Origin of the core-level binding energy shifts in Au nanoclusters
2017 (English)In: Physical Review B, ISSN 2469-9950, E-ISSN 2469-9969, Vol. 95, no 24, article id 245402Article in journal (Refereed) Published
Abstract [en]

We investigate the shifts of the core-level binding energies in small gold nanoclusters by using ab initio density-functional-theory calculations. The shift of the 4f states is calculated for magic-number nanoclusters in a wide range of sizes and morphologies. We find a nonmonotonous behavior of the core-level shift in nanoclusters depending on the size. We demonstrate that there are three main contributions to the Au 4f shifts, which depend sensitively on the interatomic distances, coordination, and quantum confinement. They are identified and explained by the change of the on-site electrostatic potential.

Place, publisher, year, edition, pages
AMER PHYSICAL SOC, 2017
National Category
Theoretical Chemistry
Identifiers
urn:nbn:se:liu:diva-138891 (URN)10.1103/PhysRevB.95.245402 (DOI)000402654300006 ()
Note

Funding Agencies|Knut and Alice Wallenberg Foundation [2012.0083]; Strong Field Physics and New States of Matter (COTXS); Ministry of Education and Science of the Russian Federation [14.Y26.31.0005]; Swedish Government Strategic Research Area in Materials Science on Functional Materials at Linkoping University [2009 00971]

Available from: 2017-06-27 Created: 2017-06-27 Last updated: 2018-03-15

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