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

The stable structure of Mo 2 Ga 2 C was determined by using a combination of crystal structure searching technique and first-principles calculations. Mo 2 Ga 2 C crystallizes a hexagonal layered structure of space group P6 3 / m m c (No. 194), which is the typical structure of conventional M n+1 AX 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 Mo 2 Ga 2 C is investigated by analyzing the stability of chemical bonds under tensile and shear deformations. Layered structural stability of Mo 2 Ga 2 C is determined by the strength of covalent Mo–Ga bond under tensile and shear strains. The stress–strain relationships of Mo 2 Ga 2 C are evaluated and compared with Mo 2 GaC. Two-dimensional layered Mo 2 C can be obtained by the selective removal of Ga atoms from Mo 2 Ga 2 C. Theoretical prediction of monolayer Mo 2 C is metallic, and has potential application as anode and thermoelectric material.