Local structure of perovskites ReO3 and ScF3 with negative thermal expansion: interpretation beyond the quasiharmonic approximation

16th International Conference on X-ray Absorption Fine Structure

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

Institute of Solid State Physics, University of Latvia, Kengaraga Str. 8, Riga

LV-1063, Latvia^1

IFN-CNR, Institute for Photonics and Nanotechnologies, Unit FBK-Photonics of Trento, Trento, Povo, Italy^2

Physics Department, Faculty of Science, Suez Canal University, Ismailia, Egypt^3

关键词: Ab initio;    Ab initio calculations;    Dynamics calculations;    Expected values;    Infrared spectrum;    Linear combination of atomic orbitals;    Local structure;    Vibration properties;   

Others  :  https://iopscience.iop.org/article/10.1088/1742-6596/712/1/012013/pdf
DOI  :  10.1088/1742-6596/712/1/012013

来源: IOP

【 摘 要 】

We propose an approach beyond the quasiharmonic approximation for interpretation of EXAFS and XRD data and for ab initio calculations of electronic and vibration properties of materials with negative thermal expansion. Ab initio electronic structure and lattice dynamics calculations for cubic and distorted ScF3were performed using the linear combination of atomic orbitals (LCAO) method. The band gap obtained in calculations for ScF3is equal to 10.54 eV and agree well with the expected value. The calculated infrared spectra of F displaced (FD) cubic ScF3allow us to predict that its mean Sc-F-Sc angle within NTE deviates from 180 degree.