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Highly Efficient Free Energy Calculations of the Fe Equation of State Using Temperature-Dependent Effective Potential Method
Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, Faculty of Science & Engineering.
Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, Faculty of Science & Engineering.
Linköping University, Department of Physics, Chemistry and Biology. Linköping University, Faculty of Science & Engineering.
Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, Faculty of Science & Engineering.
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2016 (English)In: Journal of Physical Chemistry A, ISSN 1089-5639, E-ISSN 1520-5215, Vol. 120, no 43, 8761-8768 p.Article in journal (Refereed) Published
Abstract [en]

Free energy calculations at finite temperature based on ab initio molecular dynamics (AIMD) simulations have become possible, but they are still highly computationally demanding. Besides, achieving simultaneously high accuracy of the calculated results and efficiency of the computational algorithm is still a challenge. In this work we describe an efficient algorithm to determine accurate free energies of solids in simulations using the recently proposed temperature-dependent effective potential method (TDEP). We provide a detailed analysis of numerical approximations employed in the TDEP algorithm. We show that for a model system considered in this work, hcp Fe, the obtained thermal equation of state at 2000 K is in excellent agreement with the results of standard calculations within the quasiharmonic approximation.

Place, publisher, year, edition, pages
American Chemical Society (ACS), 2016. Vol. 120, no 43, 8761-8768 p.
National Category
Theoretical Chemistry
Identifiers
URN: urn:nbn:se:liu:diva-132993DOI: 10.1021/acs.jpca.6b08633ISI: 000387198600028PubMedID: 27700093OAI: oai:DiVA.org:liu-132993DiVA: diva2:1054707
Note

Funding Agencies|Swedish Foundation for Strategic Research (SSF) program SRL [10-0026]; Swedish Research Council (VR) [2015-04391, 2014-4750, 637-2013-7296]; Swedish Government Strategic Research Area in Materials Science on Functional Materials at Linkoping University [2009 00971]; Ministry of Education and Science of the Russian Federation [14.Y26.31.0005]; PRACE-2IP project [FP7 RI-283493]

Available from: 2016-12-09 Created: 2016-12-07 Last updated: 2017-04-24Bibliographically approved
In thesis
1. Development and applications of theoretical algorithms for simulations of materials at extreme conditions
Open this publication in new window or tab >>Development and applications of theoretical algorithms for simulations of materials at extreme conditions
2017 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Materials at extreme conditions exhibit properties that differ substantially from ambient conditions. High pressure and high temperature expose anharmonic, non-linear behavior, and can provoke phase transitions among other effects. Experimental setups to study that sort of effects are typically costly and experiments themselves are laborious. It is common to apply theoretical techniques in order to provide a road-map for experimental research. In this thesis I cover computational algorithms based on first-principles calculations for high-temperature and high-pressure conditions. The two thoroughly described algorithms are: 1) the free energy studies using temperature-dependent effective potential method (TDEP), and 2) a higher-order elastic constants calculation procedure. The algorithms are described in an easy to follow manner with motivation for every step covered.

The Free energy calculation algorithm is demonstrated with applications to hexagonal close-packed Iron at the conditions close to the inner Earth Core’s. The algorithm of elastic constants calculation is demonstrated with application to Molybdenum, Tantalum, and Niobium. Other projects included in the thesis are the study of effects of van der Waals corrections on the graphite and diamond equations of state.

Abstract [sv]

Material vid extrema förhållanden uppvisar egenskaper som skiljer sig avsevärt från omgivningsförhållanden. Högt tryck och hög temperatur exponera anharmonicity, icke-linjärt beteende, och kan framkalla fasövergångar bland andra effekter. Experimentella uppställningar för att studera denna typ av effekter är vanligtvis dyra och experiment själva är mödosam. Det är vanligt att tillämpa teoretiska metoder för att ge en färdplan för experimentell forskning. I denna avhandling täcker jag beräkningsalgoritmer baserat på första principer beräkningar för hög temperatur och högt tryck. De två grundligt beskrivna algoritmer är: 1) den fria energin studier med temperaturberoende effektiv potentiell metod (TDEP), och 2) en högre ordning elastiska konstantberäkningsproceduren. Algoritmerna beskrivs i en lätt att följa sätt med motivation för varje steg som omfattas.

Den fria energiberäkningsalgoritm visas med program till hexagonal tätpackad järn på villkoren nära jordens inre kärna. Algoritmen av elastiska konstanter beräkning demonstreras med tillämpning till molybden, tantal, och niob. Andra projekt som ingår i avhandlingen är effekterna av van der Waals-korrigeringar på tillståndsekvation och elastiska konstanter i grafit och diamant.

Place, publisher, year, edition, pages
Linköping: Linköping University Electronic Press, 2017. 85 p.
Series
Linköping Studies in Science and Technology. Dissertations, ISSN 0345-7524 ; 1844
National Category
Condensed Matter Physics Other Physics Topics Atom and Molecular Physics and Optics Other Materials Engineering Theoretical Chemistry
Identifiers
urn:nbn:se:liu:diva-136447 (URN)10.3384/diss.diva-136447 (DOI)9789176855430 (ISBN)
Public defence
2017-04-28, Planck, Fysikhuset, Campus Valla, Linköping, 10:15 (English)
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Available from: 2017-04-10 Created: 2017-04-10 Last updated: 2017-04-21Bibliographically approved

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Mosyagin, IgorHellman, OlleOlovsson, WeineSimak, SergeyAbrikosov, Igor
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