Eur. Phys. J. B (2014) 87: 295
https://doi.org/10.1140/epjb/e2014-50570-9

Regular Article

Ab initio calculations of mechanical properties in β-MH_2−xHe_x (M = Er, Sc)

¹ School of Physical Electronics, University of Electronic Science and Technology of China, Chengdu 610054, P.R. China
² Department of Physics and Engineering Technology, Sichuan University of Arts and Science, Dazhou 635000, P.R. China
³ Institute of Nuclear Physics and Chemistry, China Academy of Engineering Physics, Mianyang 621900, P.R. China
⁴ Department of Nuclear Engineering and Radiological Sciences, University of Michigan, Ann Arbor, MI 48109, USA

^a e-mail: yanglildk@uestc.edu.cn

Received: 22 August 2014
Received in final form: 16 October 2014
Published online: 8 December 2014

Abstract

The ³He (helium) accumulation due to tritium decays in rare-earth metal tritides can influence their mechanical properties and stabilities, limiting their applications as neutron generators. Ab initio calculations based on density functional theory have been performed to investigate the elastic constants, bulk modulus, shear modulus and Young’s modulus of the β-MH_2−xHe_x (M = Er, Sc) systems, with the variety of the x (the ratio of He to M atoms), ranging from 0 to 0.1875. The changes in the mechanical properties of β-ErH_2−xHe_x and β-ScH_2−xHe_x exhibit two regimes, which is in agreement with the experimental observations. It appears that the different He concentrations cause the different interactions between metal atoms and their neighbors in β-MH_2−xHe_x, a key factor which gives rise to the observed two regimes. When x is about 0.13, the mechanical properties of metal hydrides degrade significantly. Furthermore, the degradation mechanisms of the mechanical properties in the β-MH_2−xHe_x systems depend mainly on the crystal structure of metal hydrides.