The structural and electronic properties of (CdSe) n (1 ≤n ≤5) clusters are calculated using density functional theory within the pseudopotential and generalized gradient approximations. The calculated binding energies and highest occupied molecular orbital2lowest unoccupied molecular orbital gaps are compared with those obtained within local density approximation.

The ground state energies of three-electron quantum dots in a strong magnetic field are calculated by both the Hartree-Fock (HF) and the numerical diagonalization methods. The electron correlation effects on the ground state energies of the dots are investigated by comparing the results from these two approaches. It is shown that the contribution of the correlations to the ground-state energies is almost negligible and the HF approximation is reliable in this case. But the correlation effects on the magmetic fields at which the ground-state momentum quantum number transitions occur are apparent The reason is also analysed.

The low-lying excitation energy spectra of two, three and five quantum dot electrons with harmonic model interactions in a large magnetic field are calculated by the Hartree-Fock (HF) methods. Correlation effects on the energy level structures are investigated by comparing the HF results with the exact ones. It is found that the pure collective excitations (center-of-mass mode quanta) existing in the exact energy spectra do not appear in the HF energy spectra. The degeneracies of energy levels are also related to the correlation interactions, especially in the energy spectrum of two electrons. In the cases of more than two electrons, as the electron-electron interaction strength is increased the HF energy levels exhibit more complex crossings than the exact ones.

The structural and electronic properties of HgmTen (m