Selected properties of beryllium clusters in ab initio model approximations

Abstract

Results of ab initio self-consistent field calculations are reported for electronic states of beryllium clusters comprised of 13, 19, 21, 33, 39, 51, 57, and 63 atoms. The clusters correspond to the second through ninth coordination shells of a central Be atom with internuclear separations taken from the lattice constants of the bulk hcp metal. Effective core potentials have been employed to replace the 1s core electrons, thereby reducing the complexity of the calculations. In addition, the use of the full D/sub 3h/ point group symmetry of each cluster results in substantial reductions of the number of two-electron integrals that must be computed and processed. Properties are calculated for selected electronic states and include binding energy, orbital energies, electric field gradient, nuclear-electron potential, diamagnetic shielding constant, second moments, and Mulliken populations. Overall net charges, second moments, and nuclear potentials become approximately constant in the larger clusters, indicating bulk behavior.