Pressure dependent mechanical properties of calcium carbides

The mechanical properties of newly synthesized Ca2C3 and Ca2C under pressure have been studied by using the first-principles calculations with generalized gradient approximation. The equilibrium geometry, elastic stiffness constants, various moduli, and Pugh's ratio of the C2/m phase of Ca2C3 and the C2/m and Pnma phases of CaC2 are systematically studied. The elastic stiffness constants of C2/m-Ca2C3 under 0-30GPa, C2/m-Ca2C under 0-7.5 GPa, and Pnma-Ca2C under 7.5-30 GPa satisfy the Born−Huang mechanical criteria. The three phases of calcium carbides exhibit ductile characteristics. The surface constructions of bulk and Young's moduli illustrate the mechanical anisotropy of Ca2C3 and Ca2C. Our results are consistent with previously obtained experimental and theoretical data and have significant implications for the application of calcium carbides.