ELECTRONIC-STRUCTURE OF SMALL GAAS CLUSTERS .2.

The electronic and geometrical structures of GaxAsy(x + y = 3-10) clusters in nonstoichiometric (x not-equal-to y) compositions have been calculated using the local-spin-density method. The results show that all even-numbered GaxAsy(x + y = even) clusters have closed shell electronic structures. The calculated ionization potential and electron affinity for the even-numbered clusters are distinctively different from the neighboring odd-numbered clusters, forming an even/odd alternating pattern with increasing cluster size. This calculation, combined with the results from an earlier calculation for stoichiometric compositions (x = y), shows that the electronic ground states of even-numbered gallium arsenide clusters in the size range 4-10 atoms are closed-shell singlet states with a substantial highest occupied molecular orbital-lowest unoccupied molecular orbital (HOMO-LUMO) gap.