Dispersion-Corrected Density Functional Theory and Classical Force Field Calculations of Water Loading on a Pyrophyllite(001) Surface

Abstract

Water adsorption on the (001) surface of pyrophyllite [Al(OH)(Si2O5)] was investigated using density functional theory (DFT) with dispersion corrections and force field calculations. The DFT calculations show that a water molecule can bind either to one or to two basal oxygen atoms of the surface, with adsorption energies varying from −0.10 to −0.19 eV depending on the binding configuration and binding site. Because the water–water interactions are stronger than the water–surface interactions, the energetically preferred structures with two or more molecules on the surface are clusters reminiscent of their gas-phase counterparts. The trend in water–surface binding energies with the number of water molecules obtained from force field calculations qualitatively agrees with that predicted by the dispersion-corrected DFT calculations. However, the force field calculations give a low-energy structural motif with a water molecule coordinated to a hydroxyl group associated with the octahedral layer of the pyroph...