The accurate determination of relative phase stabilities
using
DFT methods is a significant challenge when some of these can vary
by only a few kJ/mol. Here, we demonstrate that for a selection of
oxides (TiO2, MnO2, and ZnO) the inclusion of
dispersion interactions, accomplished using the DFT-D3 correction
scheme, allows for the correct ordering and an improved calculation
of the energy differences between polymorphic phases. The energetic
correction provided is of the same order of magnitude as the energy
difference between phases. D3-corrected hybrid functionals systematically
yield results closest to experiment. We propose that the inclusion
of dispersion interactions makes a significant contribution to the
relative energetics of polymorphic phases, especially those with different
densities, and should therefore be included for calculations of relative
energies using DFT methods.