MODELING BULK BERYLLIUM THROUGH FIRST PRINCIPLES CLUSTER STUDIES

Ab initio quantum chemical studies have been carried out on clusters o f beryllium atoms to investigate the transition between cluster- and b ulk-like behavior. The calculations and subsequent analyses have been performed on clusters ranging in size from 13 to 135 atoms. The resear ch has proceeded over the past 15 years with the sizes of clusters inv estigated increasing in parallel to advances in computing technology e mploying computers ranging from IBM mainframes in the 1970's to Gray Y -MP supercomputers in the 1990's. In addition to state-of-the-art comp uting resources, the calculations are made tractable using software in corporating effective core potentials, point group symmetry, and the s upermatrix self-consistent field theory formulation. The largest clust er investigated (135 beryllium atoms) required the computation of 199 million multicenter integrals on a Gray Y-MP. Analyses of calculated p roperties, electron populations, electron densities, and density of st ates distributions clearly show the onset of bulk behavior as cluster size increases.