Theoretical investigation on thermodynamics and stability of anti-perovskite MgCNi3 superconductor

Abstract Density functional theory (DFT) and ab initio molecular dynamics (AIMD) are performed to study the vibrational, mechanical, and thermodynamic properties (including melting point) of anti-perovskite MgCNi3 superconductor. Considering the explicit influence of the anharmonic effect on physical properties, such as thermodynamics and stability, the stable phonon spectrum can be obtained by phonon quasi-particle approximation. We also point out that MgCNi3 meets the mechanical stability conditions and exhibits ductility. Thermodynamic parameters with the change of temperature are calculated more accurately by the renormalized force constants (including the anharmonic effect). The melting point of the cubic anti-perovskite MgCNi3 is predicted to be about 2700 K.