Ab initio molecular dynamics simulations of the Sc K-edge EXAFS of scandium trifluoride

16th International Conference on X-ray Absorption Fine Structure

Bocharov, Dmitry^1,2 ; Krack, Matthias^1 ; Kalinko, Aleksandr^2 ; Purans, Juris^2 ; Rocca, Francesco^3 ; Ali, Shehab E.^4 ; Kuzmin, Alexei^2

Paul Scherrer Institute, Laboratory for Reactor Physics and Systems Behaviour, Villigen

CH-5232, Switzerland^1

Institute of Solid State Physics, University of Latvia, Kengaraga street 8, Riga

LV-1063, Latvia^2

IFN-CNR, Institute for Photonics and Nanotechnologies, Unit FBK-Photonics of Trento, Povo, Trento, Italy^3

Physics Department, Faculty of Science, Suez Canal University, Ismailia, Egypt^4

关键词: Ab initio molecular dynamics simulation;    Fluorine atoms;    Harmonic approximation;    Increasing temperatures;    Local structure;    Simple cubic;    Strong anisotropy;    Temperature range;   

Others  :  https://iopscience.iop.org/article/10.1088/1742-6596/712/1/012009/pdf
DOI  :  10.1088/1742-6596/712/1/012009

来源: IOP

【 摘 要 】

Scandium fluoride ScF3has a simple cubic structure and attracts attention due to its large negative thermal expansion (NTE) over a wide range of temperatures (0-1100 K). In this study we present ab initio molecular dynamics (AIMD) simulations of ScF3and their validation using the Sc K-edge EXAFS spectra in the temperature range from 300 K to 1000 K measured at the XAFS beamline of ELETTRA. The obtained results allow an assessement of the employed AIMD model and provide insight into the local structure and the lattice dynamics of ScF3beyond the harmonic approximation. A strong anisotropy of the fluorine atom vibrations in the direction orthogonal to the -Sc-F-Sc- chain is observed. An expansion of the ScF6octahedra is found upon increasing temperature despite of the overall NTE of the crystal.