We examine optical and energy-loss data on a variety of metals in light of a recently proposed two-carrier model of metallic optical conductivity in which the two carriers are electrons located in crystallites and in grain boundaries, respectively. We find that many of the published measurements of optical properties of metals appear to be strongly influenced by sample crystallinity and that these measurements support this simple model.

• Received 5 February 1975

DOI:https://doi.org/10.1103/PhysRevB.12.6002