SITE-SPECIFIC ANALYSIS OF RESPONSE PROPERTIES OF SODIUM CLUSTERS

A scheme we have formulated recently for partitioning the total dipole moments and polarizabilities of finite systems into site-specific contributions is used to analyze the structure-/shape- and size-specific aspects of the dipole moments and polarizabilities of small sodium clusters. The procedure is based on dividing the system volume into cells associated with its atoms. The site-specific, or atomic, dipole moments and polarizabilities are computed from the charge densities within the individualcells (“atomic volumes”) and the changes in these densities in response to an external electric field. The atomic dipole moments and polarizabilities are further partitioned into local (or “dipole”) and “charge-transfer” components. It is shown that the polarizabilities associated with the individual Na atoms vary considerably with the structure/shape of the cluster and the location of the atom within a given structure. Surface atoms, especially those at edges, have larger polarizabilities than interior atoms. The contribution of the charge-transfer components to the total polarizability increases with the cluster size.