FIRST-PRINCIPLES STUDIES OF X<sub>2</sub>FeSi HEUSLER ALLOYS

Abstract

The characteristics related to electricity and magnetism in Heusler alloys with both full (L21) and inverse (XA) structures X2FeSi (X = Mn, V) have been studied within the framework of the Density Functional Theory. Three different methods, namely LDA, GGA, and SCAN, were used to perform calculations. The aim was to investigate the energy stability of the L21 and XA structures for these compositions. The findings revealed that the XA structure is energetically stable for both structures. The choice of functional is indicated does not have a qualitative effect on the energy stability of the phases. Based on calculations, it was found that meta-GGA (SCAN) more accurately describes the electronic properties of these alloys. In the process of the calculations, it was found that these compounds are semimetals. An analysis was conducted from a local environment perspective to investigate and understand the reasons behind the semi-metallic band gap and the variations in electronic and magnetic properties observed in Heusler compounds. Calculations also showed that the magnetic moment Mn2FeSi for both structures was 1.99 µB/f.u. With regard to V2FeSi, µ = 2.00 µB/f.u. for structure XA and µ = 2.37 µB/f.u. for structure L21. These calculations are consistent with the Slater-Pauling rule for the XA structure.