Computational Requirements for Simulating the Structures and Proton Activity of Silicaceous Materials.

Structures of disiloxane and silanol and the energetics of their protonation, deprotonation, and proton exchange reactions have been studied with 14 density functionals in combination with eight basis sets. The geometries optimized by these 112 density functional methods are compared to those obtained by the second-order Møller-Plesset perturbation theory and the coupled cluster method, and the performance of all these methods on energetics is evaluated with benchmark Weizmann-1w results. The most accurate density functional for both geometries and energetics is M05-2X. Polarized augmented triple-ζ basis sets are found to be about a factor of 3-4 more accurate than polarized augmented double-ζ basis sets.