Possible monoclinic distortion of Mo2GaC under high pressure

In this work, we present high-pressure diffraction results of the Mo-based M-n (+) (1)AX(n) phase, Mo2GaC. A diamond anvil cell was used to compress the material up to 30 GPa, and x-ray diffraction was used to determine the structure and unit cell parameters as a function of pressure. Somewhat surprisingly, we find that, at 295 +/- 25 GPa, the bulk modulus of Mo2GaC is the highest reported of all the MAX phases measured to date. The c/a ratio increases with increasing pressure. At above 15 GPa, a splitting in the (1 0 0) reflection occurs. This result, coupled with new density functional theory calculations, suggests that a second order phase transition to possibly a mixture of hexagonal and monoclinic structures may explain this splitting. Such experimentally and theoretically supported phase transitions were not predicted in previously published calculations.Funding Agencies|Knut and Alice Wallenberg (KAW) FoundationKnut &amp; Alice Wallenberg Foundation; Swedish Research CouncilSwedish Research Council [642-2013-8020]; National Science Foundation (NSF)National Science Foundation (NSF) [DMR-1729335]</p