Electronic structure effects on the phase stability of B2 FeV

Recently we predicted, using classical molecular dynamics, that a known dynamical instability in the BCC-based B2 phase of the alloy iron-vanadium (FeV) at 0 K disappears at elevated temperature due to phonon anharmonicity. In this talk we will present density functional theory (DFT) results that elucidate the causes at the electronic structure level. First, we study the effects of pressure on a 2-atom cell of B2 FeV. The momentum-projected density of states (eDOS) is calculated and the charge in the e_g and t_2g orbitals is extracted upon compression. The band structure for both spin-up and spin-down is computed and a change is observed at the X and Γ high symmetry points upon compression. Second, we use Born-Oppenheimer molecular dynamics to investigate a 16-atom supercell of FeV and both the momentum-projected eDOS and the charge in the e_g and t_2g orbitals as a function of temperature were calculated. The value of the asphericity, defined as the ratio between the charge in the t_2g and e_g orbitals, is correlated to the mechanical stability of the bcc structure. We observe that the value of the asphericity decreases with pressure, destabilizing the B2 phase, but increases with temperature, stabilizing the B2 phase.