Electronic entropy in Green's-function calculations at finite temperatures

TL;DR

This paper introduces a simplified method for calculating electronic entropy in Green's function approaches at finite temperatures, avoiding complex contour integrations and addressing multivalued logarithm issues.

Contribution

It presents a new, straightforward expression for electronic entropy that overcomes previous technical challenges in Green's function calculations at finite temperatures.

Findings

The new formalism accurately computes electronic entropy without complex contour integrations.

Application to model systems demonstrates the method's effectiveness.

The approach is successfully applied to disordered bcc iron with local magnetic moments.

Abstract

We revise critically existing approaches to evaluation of thermodynamic potentials within the Green's function calculations at finite electronic temperatures. We focus on the entropy and show that usual technical problems related to the multivalued nature of the complex logarithm can be overcome. This results in a simple expression for the electronic entropy, which does not require any contour integration in the complex energy plane. Properties of the developed formalism are discussed and its illustrating applications to selected model systems and to bcc iron with disordered local magnetic moments are presented as well.