Dynamical stability and high pressure phases of platinum carbide

Using the density-functional linear response method, we study the dynamical properties of ground state zinc-blende and high pressure NaCl phases of platinum carbide (PtC). The calculated phonon dispersion curve does not show any soft modes for all wave vectors, indicating the dynamic stability of the ground state zinc-blende phase. The high pressure rock-salt phase exhibits imaginary frequencies, practically along all directions of the Brillouin zone, which means that PtC cannot exist in the NaCl phase at least up to a high pressure of 100 GPa.