First Principles Study on the Point Defects of Compound FeMnP<sub>0.67</sub>Si<sub>0.33</sub>

This study is based on the density functional theory and employs the projected augmented wave method within the VASP program package. It investigates the variation of lattice constants in Fe 2 P-type compound FeMnP 0.67 Si 0.33 in the ferromagnetic (FM) and antiferromagnetic (AFM) states, with the presence of Mn and Fe vacancy defects and Mn and Fe anti-site defects. the defect formation enthalpy of compounds containing vacancy and substitution defects were calculated using the Wagner-Schottky point defect thermodynamic model. It also investigates the relationship between the equilibrium concentration of point defects and the Mn content in the compound, as well as the variation of defect equilibrium concentration with temperature T. The calculation results show that the presence of point defects in the compound affects the lattice constants. In the FM and AFM states, the formation enthalpies of Fe anti-site and Mn anti-site defects is lower than that of Fe vacancy and Mn vacancy defects. The concentration of point defects increases with increasing temperature. The calculated results provide valuable theoretical references for the experimental preparation, defect analysis, and mechanical properties improvement of the Fe 2 P-type iron-manganese-based FeMnP 0.67 Si 0.33 compound.