Ab-initio study of structural phase transitions and optoelectronic properties in BeH2 at increasing pressure

摘要

The structural stability, electronic and optical properties of BeH2 under high pressure have been studied using the density functional theory (DFT) employing full potential-linearized augmented plane wave (FP-LAPW) method. The exchange correlation functional has been solved using the generalized gradient approximation. The calculations show that BeH2 becomes unstable upon application of pressure. At a pressure of 29.40 GPa the ground state alpha-BeH2 transforms to hypothetical phase beta-BeH2 and further at a pressure of 53.77 GPa (with respect to the ground state alpha-BeH2) alpha-BeH2 transforms to gamma-BeH2. In alpha-BeH2 phase it remains as an insulator while in beta-BeH2 phase its behavior becomes metallic. But upon further increase in pressure it becomes a semiconductor in gamma-BeH2 phase. Hence the possibility of obtaining high-pressure phases with superconducting properties cannot be ruled out. There occurs a huge equilibrium volume collapse at alpha- to beta-phase transition and relatively smaller volume changes at beta- to gamma-phase transition. Our obtained value of dielectric constant (3.0) for alpha-BeH2 is in excellent agreement with earlier reported value (3.1). Also BeH2 shows anisotropic behavior in all three studied phases. (C) 2016 Elsevier Ltd. All rights reserved.