The Korringa-Kohn-Rostoker Non-Local Coherent Potential Approximation (KKR-NLCPA)

TL;DR

The paper introduces the KKR-NLCPA, an advanced method for modeling disordered electronic systems that improves upon the KKR-CPA by including non-local correlations through a self-consistent cluster approach, enabling more accurate ab-initio studies.

Contribution

It presents the KKR-NLCPA, a systematic extension of KKR-CPA that incorporates non-local correlations via a self-consistent embedded cluster, satisfying key theoretical and practical criteria.

Findings

Method remains causal and becomes exact with large clusters.

Reduces to KKR-CPA for single-site clusters.

Applicable to one-dimensional model simulations.

Abstract

We introduce the Korringa-Kohn-Rostocker non-local coherent potential approximation (KKR-NLCPA) for describing the electronic structure of disordered systems. The KKR-NLCPA systematically provides a hierarchy of improvements upon the widely used KKR-CPA approach and includes non-local correlations in the disorder configurations by means of a self-consistently embedded cluster. The KKR-NLCPA method satisfies all of the requirements for a successful cluster generalization of the KKR-CPA; it remains fully causal, becomes exact in the limit of large cluster sizes, reduces to the KKR-CPA for a single-site cluster, is straightforward to implement numerically, and enables the effects of short-range order upon the electronic structure to be investigated. In particular, it is suitable for combination with electronic density functional theory to give an ab-initio description of disordered systems. Future applications to charge correlation and lattice displacement effects in alloys and spin fluctuations in magnets amongst others are very promising. We illustrate the method by application to a simple one-dimensional model.