Regular Article

Structural, mechanical, and thermodynamic properties of R-3m ReB₄ under high pressure

¹ School of Mechanics and Optoelectronic physics, Anhui University of Science and Technology, Huainan 232001, P.R. China
² School of Physics and Optoelectronic Engineering, Xidian University, Xi’an 710071, P.R. China
³ School of Physics and Information Technology, Shaanxi Normal University, Xi’an 710062, P.R. China

^a e-mail: jianlima2005@126.com

Received: 25 June 2019
Received in final form: 18 July 2019
Published online: 11 September 2019

Abstract

The structural, mechanical, and thermodynamic properties of R-3m ReB₄ under high pressure were investigated by using the density functional theory in combination with the quasi-harmonic Debye model in this work. The calculated structure parameters and bulk moduli of R-3m ReB₄ at zero pressure are in good agreement with previous theoretical data. The calculated single crystal elastic constants and phonon spectra revealed that R-3m ReB₄ is mechanically and dynamically stable at least 100 GPa. The pressure dependence of elastic constants and elastic modulus (B, G, and E) have been determined. Based on the obtained elastic modulus, two theoretical models were used to predict the Vickers hardness of R-3m ReB₄. Furthermore, through plotting the directional dependent of bulk moduli, Young’s moduli, and shear moduli, the elastic anisotropy has been investigated in detail. Moreover, using the quasi-harmonic Debye model, some basic thermodynamical quantities such as the heat capacity, Grüneisen parameter, and the thermal expansion coefficients of R-3m ReB₄ were explored under high temperature and high pressure. The obtained results can provide valuable reference for future synthesis and application R-3m ReB₄ material.