Density-functional study of structures and electronic properties of Cd clusters

Abstract

The lowest-energy structures and electronic properties of cadmium clusters are studied by density-functional theory with the generalized gradient approximation. The equilibrium structures of ${\mathrm{Cd}}_{n}$ $(n=2--21)$ clusters are determined from a number of structural isomers, which are generated from genetic algorithm simulations with a tight-binding potential. Various close-packed structures are found for cadmium clusters. ${\mathrm{Cd}}_{n}$ clusters with $n=4,9,10,15,17,20$ show relatively high stability, which can be related to the electron shell model, and agrees with experimental results. The density of states for the magic number clusters can also be associated with the electronic shell. The theoretical ionization potentials of ${\mathrm{Cd}}_{n}$ compare well with experimental values. The size evolution of electronic properties from van der Waals to covalent and bulk metallic behavior in Cd clusters is discussed.