We report here first extensive measurements of the temperature dependence of phonon density of states of BaFe2As2, the parent compound of the newly discovered FeAs-based superconductors, using inelastic neutron scattering. The experiments were carried out on the thermal time-of-flight neutron spectrometer IN4 at the ILL on a polycrystalline sample. There is no appreciable change in the spectra between T = 10 K and 200 K, although the sample undergoes a magnetic as well as a tetragonal-to-orthorhombic structural phase transition at 140 K. This indicates a rather harmonic phonon system. Shell model lattice dynamical calculations based on interatomic potentials are carried out to characterize the phonon data. The calculations predict a shift of the Ba-phonons to higher energies at 4 GPa. The average energy of the phonons of the Ba-sublattice is also predicted to increase on partial substitution of Ba by K to Ba0.6K0.4. The calculations show good agreement with the experimental phonon spectra, and also with the specific heat data from the literature.
@article{arxiv.0807.3172,
title = {Inelastic neutron scattering and lattice dynamical calculations in BaFe2As2},
author = {R. Mittal and Y. Su and S. Rols and T. Chatterji and S. L. Chaplot and H. Schober and M. Rotter and D. Johrendt and Th. Brueckel},
journal= {arXiv preprint arXiv:0807.3172},
year = {2008}
}