Lattice dynamics of gamma -Fe.

Large single crystals of fcc iron (\ensuremath{\gamma} phase) were grown in situ and used to study the lattice dynamics of this phase of Fe by standard inelastic neutron scattering techniques. The phonon dispersion curves were measured along the [00\ensuremath{\xi}], [\ensuremath{\xi}\ensuremath{\xi}0], and [\ensuremath{\xi}\ensuremath{\xi}\ensuremath{\xi}] symmetry directions at 1428 K. A selected number of phonon frequencies were also obtained at 1227 and 1640 K. We find that the measured dispersion curves are qualitatively similar to those of Ni and ${\mathrm{Ni}}_{0.3}$${\mathrm{Fe}}_{0.7}$. The 1428-K data were used to evaluate the elastic constants, the phonon density of states, and the lattice specific heat of \ensuremath{\gamma}-Fe.