Insights into thermodynamic properties of CsCl-type HfTM (TM = Fe, Ru, Os) compounds from first-principles calculations

Abstract

In this work, we used the first-principles calculations based on density functional theory and quasi-harmonic Debye to predict the electronic structures, phonon dispersions and thermodynamic properties of HfTM (TM = Fe, Ru, Os) compounds. The obtained phonon dispersions of HfTM indicate that they are thermodynamically stable. Moreover, HfFe, HfRu and HfOs show metallic properties from the electronic structures. The bulk moduli and thermal expansion coefficients of HfTM compounds under temperature of 0 ~ 1500 K and pressure of 0 ~ 20 GPa were considered, and the results indicate that the bulk modulus reduces as the temperature increases, and thermal expansion coefficient changes quickly to temperature at low temperatures. The order of thermal expansion coefficient is HfFe > HfRu > HfOs and that of thermal stability is HfOs > HfRu > HfFe. Besides, Debye temperature is opposite to the trend of Gruneisen parameter under the same temperature and pressure.