First-principles investigation of the Ni-Fe-Al system

TL;DR

This study uses first-principles calculations and statistical mechanics to explore the phase stability, magnetic properties, and electronic correlations of the Ni-Fe-Al system across different temperatures and compositions.

Contribution

It introduces a combined ab-initio and cluster expansion approach to accurately model the thermodynamics and phase diagram of the Ni-Fe-Al system, including the verification of a miscibility gap.

Findings

Identification of a miscibility gap in the B2 phase.

Development of a comprehensive energy landscape for Ni-Fe-Al.

Insights into the interplay between structure and magnetism.

Abstract

By combining ab-initio electron theory and statistical mechanics, the physical properties of the ternary intermetallic system Ni-Fe-Al in the ground state and at finite temperatures were investigated. The Ni-Fe-Al system is not only of high technological interest, but exhibits also rich physics, e.g., a delicate interplay between structure and magnetism over a wide composition range and substantial electronic correlations which is challenging for modern electronic structure methods. The new Stuttgart ab-initio mixed-basis pseudopotential code in the generalized gradient approximation (GGA) was used to determine the energetics in the ground state. Therewith, in combination with the cluster expansion (CE) method a representation of the energy landscape at $T$=0 over the whole Gibbs triangle was elaborated. At finite temperatures, the cluster variation method (CVM) in tetrahedron approximation was employed in order to calculate the ab-initio ternary phase diagram on the bcc and fcc lattice. Thereby, a miscibility gap in the ternary B2 phase was theoretically verified.