Theoretical prediction of hexagonal ternary phase Mo2Ga2C and its evolution to layered carbide Mo2C

Abstract

The stable structure of Mo2Ga2C was determined by using a combination of crystal structure searching technique and first-principles calculations. Mo2Ga2C crystallizes a hexagonal layered structure of space group P63/ m m c (No. 194), which is the typical structure of conventional M n+1AX n phases. The dynamical and mechanical stability of the predicted structure is confirmed by the phonon dispersion and elastic constants, respectively. The structural stability of Mo2Ga2C is investigated by analyzing the stability of chemical bonds under tensile and shear deformations. Layered structural stability of Mo2Ga2C is determined by the strength of covalent Mo–Ga bond under tensile and shear strains. The stress–strain relationships of Mo2Ga2C are evaluated and compared with Mo2GaC. Two-dimensional layered Mo2C can be obtained by the selective removal of Ga atoms from Mo2Ga2C. Theoretical prediction of monolayer Mo2C is metallic, and has potential application as anode and thermoelectric material.