Possible monoclinic distortion of Mo2GaC under high pressure

Abstract

In this work, we present a high-pressure diffraction results of the Mo-based MAX 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 pressures. 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 DFT calculations, show that a second order phase transition to possibly a mixture of a hexagonal and monoclinic structures may explain this splitting. Such experimentally and theoretically supported phase transition was not predicted in previously published calculations.