The lattice dynamics of LaFeAsO_{ 1-x}F_{ x} (x=0, 0.1) and PrFeAsO_{ 1-y} (y~0.1) are investigated using inelastic x-ray scattering and ab-initio calculation. Measurements of powder samples provide an approximation to the phonon DOS, while dispersion is measured from a single crystal of PrFeAsO_{ 1-y}. A model that agrees reasonably well with all of the data at room temperature is built from results of ab-initio calculations by softening the strength of the Fe-As bond by 30%.
Categories: cond-mat.supr-con