Structural and Elastic Properties of Fe-Ge Alloys: ab initio studies

Аннотация

In this paper, with the help of the density functional theory, the structural and elastic properties of A2, B2, D0₃, and L1₂ phases of Fe_100–xGe_x alloys (12,5 ≤ x ≤ 28,125 at. %) have been studied. The electronic and full ionic relaxations were used for the investigation of crystal structures. The concentration dependencies of the atomic volumes, structural phase transition temperatures, tetragonal and rhombohedral shear moduli have been calculated. We show that the atomic volume curves correlate with the sequence of phase transitions observed experimentally: A2→B2→D0₃ (x ≤ 22 at. % of Ge content). The structural phase transition temperatures increase with the Ge concentration. The calculated tetragonal moduli for the D0₃, A2, and L1₂ structures decrease with the increasing of the Ge content, what agrees with the experimental results. The dependence of rhombohedral shear moduli as a function of Ge concentration does not change significantly with increasing Ge atoms. The C₄₄ is increased for the D0₃ phase, while for A2, B2, and L1₂, it decreases.