Model-independent extraction of dynamical information from powder diffraction data

We describe a model-independent evaluation of the possibility of extracting detailed lattice dynamical information from neutron powder diffraction data. The method, which we first reported recently [Phys. Rev. Lett. 93, 075502 (2004)], is extended to include consideration of crystal symmetry. This is exploited to reduce errors in the approach and to allow unambiguous assignment of normal modes. The experimental and computational requirements are explored, with particular attention to the use of the reverse Monte Carlo method for generating atomistic configurations. Phonon-dispersion curves, extracted from neutron total scattering data using the technique, are presented for magnesium oxide and strontium titanate. These are used to illustrate the sensitivity and limitations of this method.