A reactive force field (ReaxFF) for zinc oxide

We have developed a reactive force field (FF) within the ReaxFF framework, for use in molecular dynamics (MD) simulations to investigate structures and reaction dynamics for ZnO catalysts. The force field parameters were fitted to a training set of data points (energies, geometries, charges) derived from quantum-mechanical (QM) calculations. The data points were chosen to give adequate descriptions of (the equations of state for) a number of zinc metal and zinc oxide phases, a number of low-index ZnO surfaces and gas-phase zinc hydroxide clusters. Special emphasis was put on obtaining a good surface description. We have applied the force field to the calculation of atomic vibrational mean square amplitudes for bulk wurtzite-ZnO at 20 K, 300 K and 600 K and we find good agreement with experimental values from the literature. The force field was also applied in a study of the surface growth mechanism for the wurtzite(0 0 0 1) surface. We find that the growth behavior depends on the presence of surface steps.