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

Abstract

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 M2C and MC2 (M\u202f=\u202fOs, Ir, Pt) are investigated in tetragonal (P4/mbm), fluorite/antifluorite (Fm3m), orthorhombic (Pnnm), pyrite (Pa-3) and hexagonal (P6/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 M2C are most stable in anti-fluorite structure, while MC2 are stable in hexagonal structure. In Os2C and Pt2C, structural phase transition is predicted from antifluorite to pyrite whereas antifluorite to hexagonal in Ir2C and hexagonal to tetragonal in OsC2 and PtC2 under high pressure. Born-Huang criteria for mechanical stability are satisfied by the elastic constants of M2C and MC2. The bulk modulus of these materials is found to be high, which indicates that these materials are super hard materials.