MODELING THE PROPERTIES OF QUARTZ WITH CLUSTERS

We illustrate a cluster approach to calculate the electronic propertie s of alpha-quartz. Cluster approaches to modeling defects and other lo calized states within crystalline matter have a number of computationa l advantages when compared to traditional energy band methods. However , the implementation of cluster models has been inhibited by the poor convergence of bulk properties with cluster size. Here we illustrate r ecent developments in algorithm construction which allow one to consid er larger clusters than previously accessible. In particular, we use c lusters such as Si18O23H26 and Si25O34H32 to model quartz. We compare these cluster calculations to plane-wave-pseudopotential calculations for crystalline quartz and find very good agreement. (C) 1998 Publishe d by Elsevier Science Ltd.