Accurate Computational Thermodynamics Using Anharmonic Density Functional Theory Calculations: The Case Study of B–H Species

The thermal
decomposition of boron–hydrogen compounds is complex and multistep
and involves the formation of various intermediates. An accurate description
of the thermodynamics of the reactants, products, and intermediates
is required for an in-depth understanding of their reactivity. In
this respect, we have proceeded to the accurate determination of the
key thermodynamic functions (ΔH(T), S(T), and CP(T)) of 44 isolated
B–H molecular species involved in the decomposition of B–H
solids, with the inclusion of anharmonic effects. An excellent agreement
is observed with available experimental data. We report the analytic
expressions of these functions obtained by fitting them with NASA
functions in the 200–900 K temperature range. Because the vibrational
spectra of these species are their fingerprints, we also report the
predicted IR and Raman spectra. The calculated anharmonic spectra
show an excellent agreement with experiments and allow for a clear-cut
identification of fundamentals, combinations, and overtones.