  The band gaps and spectral shifts of CdS, CdSe, CdTe, AlP, GaP, GaAs, and InP
semiconductor clusters are calculated from band structure calculations using
accurate local and non-local empirical pseudopotentials. The effect of
spin-orbit coupling on the band structures is included in the calculations when
they are important. The complete set of pseudopotential parameters and full
computational details are reported for all these semiconductors. The calculated
spectral shifts of zinc-blende and wurtzite CdS, wurtzite CdSe, and zinc-blende
InP clusters are in good agreement with experiments over a range of cluster
sizes. The effect of crystal structure on the band gaps is small in large
clusters but becomes important in small clusters. In the absence of
experimental data, our calculations provide reasonable estimates of expected
spectral shifts for the other clusters. These results demonstrate that the
empirical pseudopotential method yields unique insights into the quantum
confinement effects and is a powerful tool for calculating the spectral shifts
of semiconductor clusters.
