Ab Initio calculation of the vibrational spectrum and thermodynamic properties of rhombohedral P4O10

TL;DR

This study uses ab initio methods to accurately compute the vibrational spectrum and thermodynamic properties of rhombohedral P4O10, providing insights into its phonon behavior and heat capacity.

Contribution

It presents the first ab initio calculation of P4O10's vibrational spectrum and thermodynamic functions, refining spectral interpretation and quantifying molecular contributions.

Findings

Calculated vibrational spectrum agrees with experimental data

Low-temperature heat capacity matches measurements with minor offset

Molecular contributions account for about 80% of heat capacity

Abstract

Plane-wave pseudopotential methods and density functional perturbation theory are used to calculate the phonon density of states and thermodynamic functions of h-P4O10. The calculated vibrational spectrum is in good agreement with the measured spectrum, but the calculations indicate some modifications in the interpretation of the spectrum, mainly suggesting changes in the number of components used to fit a few of the observed peaks. The calculated low-temperature heat capacity is in good agreement with the measured heat capacity, with a systematic offset of approximately -5 J mol-1 K-1, independent of temperature. . Comparison with molecular calculations indicate that molecular contributions make up about 80% of the heat capacity of h-P4O10