Classical Density Functional Theory Approach to the Vibrational Properties and Lattice Specific Heat of a Quasi-One-Dimensional Antiferromagnet KFeSe2

Abstract

We have performed ab initio calculations of vibrational properties of KFeSe2 compound utilizing density functional theory. Total and element specific phonon densities of states have been calculated within a direct approach of harmonic approximation. We have used phonon density of states to calculate lattice contribution to the specific heat. The calculated phonon density of states shows numerous of high-frequency vibrational modes of Fe and Se atoms, which strongly restricts application of the Debye model for analysis of the thermodynamic properties of KFeSe2. The results of this work can be used in a further estimation of the magnetic specific heat of KFeSe2.