Negative thermal expansion of ScF3: First principles vs empirical molecular dynamics
Date
2019
Authors
Bocharov, Dmitry
Rafalskij, Yuri
Krack, Matthias
Putnina, Mara
Kuzmin, Alexei
Journal Title
Journal ISSN
Volume Title
Publisher
Institute of Physics Publishing
Abstract
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.
Description
The calculations were performed on the Paul Scherrer Institute cluster Merlin4, HPC resources of the Swiss National Supercomputing Centre in Lugano (project ID s626) as well as at the Latvian SuperCluster (LASC). Authors are greatly indebted to S. Ali, D. Gryaznov, R.A. Evarestov, M. Isupova, A. Kalinko, V. Kashcheyevs, V. Pankratov, S. Piskunov, A. I. Popov, J. Purans, F. Rocca, L. Shirmane, P. Zˇguns, and Yu. F. Zhukovskii for many stimulating discussions. Financial support provided by project No. 1.1.1.2/VIAA/l/16/147 (1.1.1.2/16/I/001) under the activity “Post-doctoral research aid” realized at the Institute of Solid State Physics, University of Latvia is greatly acknowledged.
Keywords
Research Subject Categories::NATURAL SCIENCES:Physics