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MA: Fachverband Magnetismus

MA 1: Computational Magnetism I

MA 1.9: Vortrag

Montag, 16. März 2020, 11:45–12:00, HSZ 04

Ab-initio study of phase transitions in Fe100-xAlx alloys — •Vasily Buchelnikov, Mariya Matyunina, and Mikhail Zagrebin — Chelyabinsk State University, Chelyabinsk, Russia

Fe-Al-based functional materials are perspective for industrial application due to the unique combination of properties such as high strength, corrosion stability, low density, and low cost. It would be interesting to estimate structural and magnetic phase transition temperatures in the most questionable area of 10-40 at.% of Fe-Al with different structures. In this work, based on structural and magnetic phase transition temperatures estimated theoretically from the first principles, the concentration phase diagram for Fe100-xAlx (15.625<x<31.25 at.%) was plotted. Structural phase transition temperatures for the experimentally observed crystal structures were obtained from the structural optimization. It is shown that for x=28.125 at.% L12-like phase with slight distortions is energetically favorable. The ground state energy and magnetic moments of Fe75Al25 with different structures were calculated within GGA and GGA+U approaches. It is shown that in the case of GGA+U approximation, L12 phase becomes more stable compared with D03. The Curie temperatures were estimated from mean field approximation and Monte Carlo simulations using ab initio calculated exchange coupling constants. Both structural and magnetic phase transition temperatures are found in qualitative agreement with the experiment. Depending on Al concentration, five different sequences of phase transitions are observed in the phase diagram.