Critical size for a metal-nonmetal transition in transition-metal clusters.

摘要: Based on a tight-binding Friedel model for the density of d-electron states, we investigate critical size metal-nonmetal transition in transition-metal clusters. An analytic equation has been introduced cluster with close-packed structure. At point (about 30--50 atoms), states near Fermi level exceeds 1/${\mathit{k}}_{\mathit{B}}$T and discrete energy levels form quasicontinuous band. The classical conducting-sphere-droplet becomes applicable describing size-dependent ionization potential those clusters larger than size. Our estimation is supported by various experimental evidence such as threshold potential, scanning tunneling microscopy, core-level shifts.