Electrical conductivity of finite metallic systems: Disorder

The electrical conductivity of finite, three-dimensional clusters containing up to 201 atoms on an fcc lattice was calculated using a combination of density functional theory, multiple-scattering theory, and the Kubo-Greenwood equation. Isolated clusters and clusters embedded in a medium determined by the coherent-potential approximation (CPA) were investigated. Densities of states and electrical resistivities were calculated for various situations: varying numbers of configurations used for the configurational average, varying energies, different alloys, different cluster sizes, and, finally, two cluster types, namely, spherical and rectangular clusters. Cluster calculations were compared to CPA calculations based on the same alloys. From this comparison a criterion was derived when a representation of an infinite medium by finite clusters is expected to yield good results for the conductivity.