Negative thermal expansion of ScF3: first principles vs empirical molecular dynamics

Functional Materials and Nanotechnologies 2018

Bocharov, Dmitry^1 ; Rafalskij, Yuri^1 ; Krack, Matthias^2 ; Putnina, Mara^1 ; Kuzmin, Alexei^1

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

LV-1063, Latvia^1

Paul Scherrer Institut, Forschungsstrasse 111, Villigen PSI

5232, Switzerland^2

关键词: Ab initio molecular dynamics;    Atomistic simulations;    Bond-angle distribution;    Increasing temperatures;    Isobaric-isothermal;    Radial distribution functions;    Temperature dependence;    Thermal vibration;   

Others  :  https://iopscience.iop.org/article/10.1088/1757-899X/503/1/012001/pdf
DOI  :  10.1088/1757-899X/503/1/012001

来源: IOP

【 摘 要 】

The crystal lattice of cubic scandium fluorine (ScF3) exhibits negative thermal expansion (NTE) over a wide range of temperatures from 10 K to 1100 K. Here the NTE effect in ScF3 is studied using atomistic simulations based on empirical and ab initio molecular dynamics (AIMD) in the isobaric-isothermal (NpT) ensemble. The temperature dependence of the average lattice constant, the Sc-F-Sc bond angle distribution and the radial distribution functions were obtained. Crossover from the NTE to positive thermal expansion occurring at about 1100 K is reproduced by AIMD simulations in agreement with the known experiment data. At the same time, empirical MD model fails to reproduce the NTE behaviour and suggests an expansion of the ScF3 lattice with increasing temperature. However, both MD models predict strong anisotropy of fluorine atom thermal vibration amplitude, being larger in the direction orthogonal to the Sc-F-Sc atom chain.