Magnetic tight-binding and the iron-chromium enthalpy anomaly

TL;DR

This paper develops a magnetic tight-binding theory based on density functional expansion, accurately models transition metals and alloys, and explains the iron-chromium enthalpy anomaly through a simplified rigid band approach.

Contribution

It introduces a self-consistent magnetic tight-binding method derived from density functional theory and applies it to explain the iron-chromium enthalpy anomaly.

Findings

Accurately describes electronic structure of transition metals and alloys.

Provides a simple interpretation of the iron-chromium enthalpy anomaly.

Shows transferability of tight-binding parameters across transition metals.

Abstract

We describe a self consistent magnetic tight-binding theory based in an expansion of the Hohenberg-Kohn density functional to second order, about a non spin polarised reference density. We show how a first order expansion about a density having a trial input magnetic moment leads to the Stoner--Slater rigid band model. We employ a simple set of tight-binding parameters that accurately describes electronic structure and energetics, and show these to be transferable between first row transition metals and their alloys. We make a number of calculations of the electronic structure of dilute Cr impurities in Fe which we compare with results using the local spin density approximation. The rigid band model provides a powerful means for interpreting complex magnetic configurations in alloys; using this approach we are able to advance a simple and readily understood explanation for the observed anomaly in the enthalpy of mixing.