IONIZATION-POTENTIALS OF SMALL SILICON AND GERMANIUM CLUSTERS FROM THE PARAMETERIZED HAMILTONIAN METHOD

The ionization potentials (IPs) of Si-n(n = 2 - 12) clusters were calc ulated using the parameterized tight-binding method. The matrix elemen ts were obtained using the universal parameters of Harrison. Two sets of universal parameters were used for this calculation. For each clust er, several possible geometries were considered in their equilibrium c onfigurations which were determined by other previous calculations. It was found that the calculated IPs were very sensitive to the choice o f atomic energy parameters, but were not very sensitive to the choice of universal parameters. The magnitudes of the calculated IPs varied v ery much, depending on the choice of atomic energy parameters. However , except for a constant shift in energy, the general trend of all the calculated IPs seemed to explain reasonably well the trend observed in the experiments. The IPs of germanium clusters were also calculated.