Atomistic study on the structure and thermodynamic properties of Cr7C3, Mn7C3, Fe7C3

The crystal structures and stabilities of Cr7C3, Mn7C3, Fe7C3 have been investigated using the interatomic potentials obtained by the lattice inversion method. The calculated structures of Cr7C3, Mn7C3 and Fe7C3 are proposed to be hexagonal with P63mc space group and the calculated lattice constants are in basic agreement with the experimental data. The calculated cohesive energies indicate that the increase in the atomic number of the metal is accompanied by the decrease in the stability of its carbides. The phonon density of states and vibrational entropy related to dynamic phenomena are also evaluated. This work provides a new method for studying the properties of carbides with complex structure.