A first-principles study on new high-pressure metastable polymorphs of MoO2

The pressure-dependence of the stabilities of several MoO2 phases has been investigated by density functional theory (GGA/PBE/PAW). Out of a set of 15 MX2 structures, the [SnO2(II), [alpha-PbO2], and a modified rutile structure type were identified as possible metastable MoO2 polymorphs based on the analysis of thermodynamic properties and dynamic stability. High-pressure calculations suggest an orthorhombic TiO2 structure, dubbed [ortho-TiO2], as a high-pressure polymorph at around 25 GPa. Furthermore, we find that the previously reported rutile-type MoO2 may be understood as a modified rutile type similar to the [VO2] structure. (C) 2016 Elsevier Inc. All rights reserved.