We will present our new ReaxFF force-fields for zinc oxide (ZnO) and ceria (CeO2) and display their capabilities to describe bulk and surface structure, energetics and some surface reactions.
There is a large interest in finding connections between catalytic activity and nanoscale structures. Although much effort has been put into exploring the surface structures and surface reactions of catalytic metal oxides, atomistic details and mechanisms are usually very difficult to acquire. Modelling the catalyst using computers is one way to obtain detailed information. However, for computer simulations to be feasible, one is forced to either reduce the size of the model of these nanostructures or to simplify the interactions between the atoms constituting them. In this study we have chosen the latter.
Our approach is to describe the interactions with analytical functions, i.e. force-fields (FF). Here we describe the development of a force-field for zinc oxide and ceria within the reactive force-field (ReaxFF) framework [A. C. T. van Duin, S. Dasgupta, F. Lorant, W. A. Goddard III, J. Phys. Chem. A 105 (2001) 9396]. Complicated bonding situations, such as functional CeO2 or ZnO surfaces, put high demands on the complexity and quality of the FF, and ReaxFF is a bond-order model which includes explicit two-, three- and four-body interaction terms. In this study, such force-fields were derived for zinc oxide and ceria from quantum-chemical calculations for many small oxide clusters and for a number of metal and metal oxide polymorphs. |