LEVEL-SPACING DISTRIBUTION IN THE TIGHT-BINDING MODEL OF FCC CLUSTERS

A lattice-gas Monte Carlo method is used to simulate metallic fcc clus ters at finite temperatures. A tight-binding model including s and p e lectrons has been derived for reproducing the free-electron-like energ y band for the bulk metal and this model is used for calculating the e lectronic structures of the fcc cluster. The resulting level-spacing d istribution at the Fermi energy is a Wigner distribution. The width of the distribution in small clusters is smaller than that calculated fr om the bulk density of states. In the lattice gas clusters the energy gaps related to the electronic magic numbers do not show up at the Fer mi level. The energy between the last occupied and the first unoccupie d levels is, on average, larger than other level spacings near the Fer mi level.