Electronic structure calculations on alloys using the polymorphous coherent-potential approximation

Abstract

We present self-consistent calculations of the electronic density of states of disordered copper-palladium and silver-palladium alloys using the polymorphous coherent-potential approximation and the Korringa-Kohn-Rostoker coherent-potential approximation. We find that the agreement between the theoretical partial density of states of palladium d bands in copper-rich copper-palladium alloys and experiment is significantly improved when the polymorphous coherent-potential approximation is used. The densities of states of silver-palladium alloys calculated with the two versions of the coherent-potential approximation are identical and agree with experiment. This indicates that the improved treatment of Coulomb effects in the polymorphous coherentpotential approximation is necessary only for alloys such as copper palladium that have considerable charge transfer.

Coarse-grained density functional theories for metallic alloys: Generalized coherent-potential approximations and charge-excess functional theory

“…The limitation n / N Ӷ 1 that comes from the above argument does not impose any upper bound on the maximum length scale at which chemical fluctuations can be studied and it is of no practical importance provided that N is large enough to ensure a good approximation គ a c . As reported in the literature, 47,49 it seems that N of about 100 is already enough.…”

“…This notwithstanding, GCPA theories are able to predict complex trends for certain site-diagonal properties as, e.g., the site resolved DOSs. 49,52 Since Eq. ͑41͒ allows us to evaluate, among other properties, also the charge density of each fragment and, hence, the full charge density ͑r͒, then, in virtue of the Hohenberg and Kohn theorem, it follows that any ground state observable in the sample given is a functional of the set of the Madelung potentials at all the crystal sites, V i Mad ͑r͒, and of the set of the atomic numbers only.…”

Mean potential of Bethe in the classical problem of calculating bulk electrostatic potentials in crystals

“…Equation (5.12) is important if self-consistent effects of b ( ) U r on ini ( ) ρ r are explored [10,12,14,26]. Actually, the invariance of b ( ) U r in Eq.…”

“…As a consequence, the mean value of the bulk potentials averaged over the unit-cell volume turns out to be zero in this case [15,24]. It is natural that namely this type of the potential field in the bulk accounts for the charge transfer [9,[12][13][14][26][27][28] and, altogether, for the electron distribution map in crystals [6,12,29].…”

“…The summation of Coulomb potentials over crystal lattices is a classical problem [1] important for determining the cohesive energy in crystals [2][3][4][5][6][7][8][9][10], as well as for describing electronic properties there [6,8,[11][12][13][14]. Based on the Poisson summation formula, the Ewald approach [15] is powerful and reliable for practical calculations [16][17][18][19].…”