Total energy calculations of random alloys: Supercell, Connolly-Williams, and CPA methods

Abstract

We compare the results of total energy calculations obtained by three most popular methods, the supercell method, the Connolly-Williams (CW) method, and the coherent potential approximation (CPA). As a reference we use the result for a supercell of 256 atoms obtained by the order-N locally self-consistent Green's function (LSGF) method. We show that for the particular case of a fcc Ag-Au alloy there is satisfactory agreement between the different techniques. Moreover, we demonstrate that in the framework of the CPA and the screened impurity model (SIM) one may obtain a reliable description of the total energy of a random alloy.