Improved atomistic simulation of diffusion and sorption in metal oxides

Gas diffusion and sorption on the surface of metal oxides are investigated using atomistic simulations, that make use of two different force fields fo r the description of the intramolecular and intermolecular interactions. MD and MC computations' are presented and estimates of the mean residence tim e, Henry's constant, and the heat of adsorption are provided for various co mmon gases (CO, CO2 ,O-2, CH4, Xe), and semiconducting substrates that hold promise for gas sensor applications (SnO2, BaTiO3). Comparison is made bet ween the performance of a simple, first generation force field (Universal) and a more detailed, second generation field (COMPASS) under the same condi tions and the same assumptions regarding the generation of the working conf igurations. It is found that the two force fields yield qualitatively simil ar results in all cases examined here. However, direct comparison with expe rimental data reveals that the accuracy of the COMPASS-based computations i s not only higher than that of the first generation force field but exceeds even that of published specialized methods, based on ab initio computation s. (C) 2001 American Institute of Physics.