Pressure effects on the structural, elastic, magnetic and thermodynamic properties of Mn2AlC and Mn2SiC MAX phases

Abstract The inherent properties of MAX phases have made them candidate materials for various technological applications. From this perspective, the present article reports the results of a detailed theoretical investigation of the effects of pressure on the structural, elastic, magnetic, and thermodynamic properties of Mn2AlC and Mn2SiC MAX phases using density functional theory (DFT). The lattice parameter c decreases with increasing pressure slightly faster than the lattice constant a. Both of studied compounds remain mechanically stable under the pressure up to 30 GPa. All independent elastic constants increase non-linearly with increasing pressure. Mn2SiC is ductile, whereas Mn2AlC is brittle at ambient pressure. The ductility of Mn2SiC increases with increasing pressure, while Mn2AlC undergoes a transition from brittle to ductile at 10 GPa. It is found that Mn2AlC is stable in a ferromagnetic ordering of magnetic moments, while Mn2SiC is stable in an anti-ferromagnetic ordering. The magnetic moment of Mn in Mn2AlC at zero pressure is approximately 1.67 μB, which is consistent with the value of 1.86 μB reported in the literature. The high melting temperature and high Debye temperature of Mn2AlC and Mn2SiC make them suitable for use in harsh environments. Mn2AlC is a promising thermal barrier coating (TBC) material. The rate of increase of the isobaric heat capacity Cp of Mn2AlC with increasing temperature is higher than that of Mn2SiC. The thermal expansion coefficient of Mn2AlC is larger than that of Mn2SiC over all pressure and temperature ranges considered here. We hope this study will inspire MAX phase researchers around the world to further explore the properties of the title materials through experiments and theories.