Neutron scattering Measurements of the phonon density of states of   FeSe$_{1-x}$ superconductors
  Inelastic neutron-scattering experiments have been carried out on polycrystalline samples of the FeSe$_{1-x}$ superconductors. We report the phonon density of states for FeSe$_{1-x}$ with Tc$\approx$8 K. The phonon cutoff frequency is observed around 40 meV. No significant change is observed across the superconducting transition. The measurements support the published first-principles calculations [A. Subedi et al., Phys. Rev. B \textbf{78}, 134514 (2008)]. 
D. Phelan, J. N. Millican, E. L. Thomas, J. B. Leao, Y. Qiu, R. Paul