GROUND-STATE PROPERTIES AND OPTICAL-RESPONSE OF LIXNA4-X,X=0-4 - AN ABINITIO STUDY

The ground state properties of LixNa4-x (x = 0-4) were investigated using extended basis Hartree-Fock calculations. The existence of substitution isomers was found for the mixed alkali clusters and planar singlet ground states were found for all clusters, including the isomers. The optical response of the clusters was modeled via configuration interaction-singles (CIS) in the hope of helping to interpret the experimental data. CIS results were found comparable to experiment at lower excitation energies, but inadequate at higher energies due to the neglect of doubles and higher excitations. Some exploration of the excited state surfaces of Li-4 and of one isomer of Li2Na2 is also reported. Comparisons are made between CIS calculations, experiment, and multireference doubly excited configuration interaction calculations.