First-Principles Study for Thermodynamic Properties of Solid $$\hbox {KNO}_{2}$$ KNO 2 System

Abstract

To enable us better understand the performance of molten salt energy storage in a solar thermal power system, thermodynamic properties of the solid KNO 2 system at ambient pressure and temperatures between 0 K and 711 K are determined by first-principles simulation based on density functional perturbation theory calculations with plane waves and pseudopotentials. Thermodynamic parameters of the Debye temperature, specific heat capacity at constant volume, phonon transfer speed, phonon mean free path, and phonon thermal conductivity as a function of temperature are estimated. The results show that the calculated phonon thermal conductivity is in good agreement with experimental values, but the calculated specific heat capacity at constant volume is lower than measured values. The isometric specific heat capacity of KNO 2 is 75.03 J·mol −1 ·K −1 , and the phonon thermal conductivity is 2.37 W·m −1 ·K −1 at ambient temperature.