Are random metallic alloys charge glasses?

Abstract

The charge excess functional (CEF) theory allows for very accurate calculations of the distribution of excess charges (DOC) in metallic alloys. We present CEF results for Cu_0.50 Zn_0.50 alloys and study the effects of substitutional disorder on the corresponding DOCs. In ordered metallic compounds the site charge excesses assume values in a discrete set, while in random alloys they can take any value in some finite interval. We show that the width of the DOC is strongly correlated with the short-range order parameter and, hence, order–disorder phase transitions can be viewed as transitions from a monodisperse to a polydisperse regime for the DOCs. In substitutionally disordered alloys the polydisperse DOCs imply polydispersivity for the interatomic interaction strengths too, thus suggesting an analogy with topologically disordered systems.