Self-consistent supercell approach to alloys with local environment effects

TL;DR

This paper introduces a supercell-based method that accurately models local environment effects in random alloys, improving electronic structure calculations by combining Green's function techniques with self-consistent effective media.

Contribution

It generalizes the LSGF technique within the EMTO framework to efficiently account for local environment effects in alloy electronic structure calculations.

Findings

Accurately models local environment effects in alloys.

Demonstrates importance for magnetic and bulk properties.

Shows linear scaling with supercell size.

Abstract

We present an efficient and accurate method for calculating electronic structure and related properties of random alloys with a proper treatment of local environment effects. The method is a generalization of the locally self-consistent Green's function (LSGF) technique for the exact muffin-tin orbital (EMTO) method. An alloy system in the calculations is represented by a supercell with a certain set of atomic distribution correlation functions. The Green's function for each atom in the supercell is obtained by embedding the cluster of neighboring atoms lying within a local interaction zone (LIZ) into an effective medium and solving the cluster Dyson equation exactly. The key ingredients of the method are locality, which makes it linearly scaling with the number of atoms in the supercell, and coherent-potential self-consistency of the effective medium, which results in a fast convergence of the electronic structure with respect to the LIZ size. To test the performance and accuracy of the method, we apply it to two systems: Fe-rich bcc-FeCr random alloy with and without a short-range order, and a Cr-impurity on the Fe surface. Both cases demonstrate the importance of taking into account the local environment effects for correct description of magnetic and bulk properties.