Specific heat at constant pressure from first principles: contributions from fully anharmonic vibrations

Abstract

Specific heat at constant pressure (Cp) for diamond Si and wurtzite GaN is calculated using a novel, first principles method based on density functional theory. This method, termed the Beyond Quasi-Harmonic method, completely takes into account all anharmonic vibrations–both from changes in volume and phonon interactions. Our calculated values for Si show excellent agreement with the generally accepted experimental values. For GaN, however, there is a large discrepancy between two sets of experiments. From an analysis of the available literature, and our own data we develop a set of recommended values.