Nonmetal-metal transition in Rh-N and Ru-N clusters

The nonmetal-metal transition in Rh-N and Ru-N clusters is studied by using a cl-electron tight-binding Hubbard Hamiltonian including Coulomb interact ions in the unrestricted Hartree-Fock approximation The nonmetal-metal tran sition occurs when the density of states at the Fermi level exceeds 1/k(B)T and the discrete energy levels begin to form a quasi-continuous band. The role of the cluster structure is investigated by performing calculations fo r fee and bce geometries. The critical size for the nonmetal-metal transiti on in the clusters decreases fast with increasing T and at the liquid nitro gen temperature (T= 77 K) the critical size is of the order of 60 to 80 ato ms. (C) 2000 Published by Elsevier Science B.V, All rights reserved.