Screening, charge distribution, and electron correlations in metallic alloys

We study a model of charge transfer in alloys proposed by Bruno, Zingales, and Wang Phys. Rev. Lett. 91, 166401 2003 and show its connection with electron-electron correlations. We then investigate in detail the properties of Madelung and related matrices, the mechanism leading to the screening of the electrostatic interactions between atomic net charges in random alloys, and calculate the screened interactions. Furthermore, we derive an expression for the total energy and show that the fluctuation contributions to the local and Madelung energy mutually cancel. We then derive and discuss the probability distribution function of local charges and make a comparison with calculations for large supercells. Finally, we discuss the relation of the present approach to other theories aimed at the description of Coulomb effects in alloys.