Effects of composition, temperature, and magnetism on phonons in bcc Fe-V alloys

The phonon densities of states of body-centered-cubic Fe-V alloys across the full composition range were studied by inelastic neutron scattering, nuclear resonant inelastic x-ray scattering, and ab initio calculations. The average phonon energy followed the inverse of the electronic heat capacity and the inverse of the electronic density of states at the Fermi level, showing how the interatomic forces depend on electronic screening. These quantities, including phonon energy, changed rapidly near the composition of the paramagnetic- ferromagnetic transition. For Fe- and V-rich alloys, the thermal phonon softening deviated from quasiharmonic behavior but better agreement was found for intermediate compositions. The Fe partial phonon density of states has a distinctly different shape than V for alloys with less than 50 at.% Fe.