Vibrational properties and lattice specific heat of RbFeS2

In the present study, we have performed ab initio calculations of vibrational properties of RbFeS2 compound utilizing density functional theory. Total and element specific phonon densities of states (PDOS) were calculated within a direct approach of harmonic approximation. We used phonon density of states to calculate lattice contribution to the specific heat. The calculated phonon density of states shows a large number of high-frequency vibrational modes of Fe and S atoms, which strongly restricts application of the Debye model for analysis of thermodynamical properties of RbFeS2. The results of the present paper could be used in a further estimation of magnetic specific heat of RbFeS2.