Effects of long-range interactions in cyclic cluster calculations of metal oxides

Abstract

The effect of long-range Coulomb interactions on bulk and surface properties calculated within the cyclic cluster model is investigated for the oxides MgO, TiO2, V2O5, and α-Al2O3. The Madelung potential is calculated with the Ewald summation method. Results of semiempirical calculations using free clusters, cyclic clusters with and without Madelung potential are compared with each other and with available experimental data from the literature. For the cubic system MgO the effect of long-range interactions on calculated binding energies and structure parameters is small, indicating that the Madelung sum is rapidly converging. On the other hand, the inclusion of lattice sums is of high importance for the simulation of anisotropic systems using the cyclic cluster model. The convergence of calculated properties with increasing cluster size is considerably improved by introducing Madelung sums. Therefore, it is possible to use moderately small cyclic clusters to model the bulk and surface properties of a variety of systems with reasonable accuracy.