First principles study of structural, electronic and mechanical properties of metal carbides M2C and MC2 (M= Os, Ir, Pt)

Abstract The search for hard refractory materials has recently been attractive in the field of material science. The structural stability, electronic structure, and mechanical properties of noble metal carbides M 2 C and MC 2 (M = Os, Ir, Pt) are investigated in tetragonal ( P 4/ mbm ), fluorite/antifluorite ( Fm3m ), orthorhombic ( Pnnm ), pyrite ( Pa-3 ) and hexagonal ( P 6/ mmm ) phases for their potential ability and use as hard materials, by the first principles calculation based on density functional theory. It is found that M 2 C are most stable in anti -fluorite structure, while MC 2 are stable in hexagonal structure. In Os 2 C and Pt 2 C, structural phase transition is predicted from antifluorite to pyrite whereas antifluorite to hexagonal in Ir 2 C and hexagonal to tetragonal in OsC 2 and PtC 2 under high pressure. Born-Huang criteria for mechanical stability are satisfied by the elastic constants of M 2 C and MC 2 . The bulk modulus of these materials is found to be high, which indicates that these materials are super hard materials.