Theoretical study of the properties of with pyrite and marcasite structures

Pyrite and marcasite structures are both potential structures of platinum nitride. The mechanical properties of these two structures are similar, so we further investigate the thermodynamic properties of platinum nitride under high pressure and high temperature by the quasi-harmonic Debye model, in which phonon effects are considered. In the paper the important thermodynamic parameters, Debye temperature and heat capacity, have been investigated. The results show that the melting point is higher and the interatomic force is stronger in the pyrite structure than in the marcasite and fluorite structures. In addition, the marcasite structure has a much higher value of C V at the same T and P , and the change in C V is much sharper than that of the pyrite structure at low temperatures. Moreover, we notice that pressure has less influence on C V .