Creation of models and parametrization of a classical force field for amorphous Al2O3/water interfaces based on Density Functional Theory

Abstract

We present realistic models of amorphous alumina/water interfaces taking into account the chemical termination with hydroxyl groups and chemisorbed water molecules, as predicted by DFT-based MD simulations. On the basis of these models we parametrize a fixed-charges force field to describe the interactions within alumina and across the alumina/water interface, which can be seamlessly combined with biomolecular force fields via straightforward combination rules. The potential parameters are fitted to DFT reference calculations of water/surface interactions and are shown to be very well transferable to organic molecules adsorbing on alumina, in particular amino acid analogues. The correct protonation/deprotonation equilibria of the surface sites in contact with water solutions at different pH values is taken into account and implemented in the surface models and force field parameters via adjustments of the atomic point charges. The ability of our models and force field to predict experimental observables is demonstrated by unbiased calculations of the heat of immersion of alumina powders and of the adsorption free energy of glutathione disulfide on alumina in comparison with experimental data.