New high-pressure phase of MgH2: An ab initio constant-pressure study


Durandurdu M.

EPL, vol.105, no.4, 2014 (Journal Indexed in SCI) identifier identifier

  • Publication Type: Article / Article
  • Volume: 105 Issue: 4
  • Publication Date: 2014
  • Doi Number: 10.1209/0295-5075/105/46001
  • Title of Journal : EPL

Abstract

The stability of magnesium hydride (MgH2) at high pressure is studied using a constant-pressure ab initio technique. Two phase transformations are successfully observed through the simulations. The rutile structure undergoes a phase transformation into a CaCl2-type phase. Further increase in pressure results into a first-order phase transition into an orthorhombic state within Pbcm symmetry. This phase can be considered as a distorted CsF2-type crystal and does not correspond to the previously proposed MgH2 phases. The transformation mechanism of the CaCl2-Pbcm phase change at the atomistic level is successfully characterized and it is found that the CaCl2-to-Pbcm phase change proceeds via an ideal CaF2-type intermediate phase. These phase transformations are also analyzed using total energy-volume calculations.Copyright (C) EPLA, 2014