Nonmetal-metal transition in Znn (n=2-20) clusters

By using density functional calculation with generalized gradient approximation, we have studied the structural and electronic properties of the zinc clusters. The lowest-energy structures of Znn (n=2-20) clusters are determined. Three kinds of growth pathways are obtained in the small zinc clusters from Zn4 to Zn8 and tetrahedron-based structures have favorable energy. The zinc clusters with 7-16 atoms are semiconductorlike. A structural transition from low coordination cagelike to high coordination compact structures is obtained around Zn17. The Znn clusters with n=4, 7, 9, 10, 14, 18, 20 show relatively high stability, consistent with the electron shell model and mass spectra. The ionization potentials of the Znn clusters are calculated and compared with conducting sphere droplet model. The size evolution of zinc clusters from van der Waals to covalent and bulk metallic behavior is discussed. The Zn clusters show stronger metallicity than the Cd and Hg clusters with same size