Role of Nonlocal Exchange in Molecular Crystals: The Case of Two Proton-ordered Phases of Ice

We present a periodic density functional theory investigation of two proton-ordered phases of ice. Their equilibrium lattice parameters, relative stabilities, formation energies, and densities of states have been evaluated. Nine exchange-correlation functionals, representative of the generalized gradient approximation (GGA), global hybrids, range-separated hybrids, meta-GGA, and hybrid meta-GGA families have been taken into account, considering two oxygen basis sets. Although the hydrogen-bond network of ice is well reproduced at the B3LYP, M06-L, or LC-wPBE levels, formation energies are only correctly evaluated with the two former functionals. Band gaps on the other hand are only quantitatively reproduced at the B3LYP level. These results indicate that this last functional, a de facto reference for molecular calculations, gives in average the most accurate results for the considered ice properties. (C) 2011 Wiley Periodicals, Inc. J Comput Chem 32: 2177-2185, 2011