Single-crystal lattice dynamics derived from polycrystalline inelastic x-ray scattering spectra

New insights into the lattice dynamics ofα-quartz

“…This shortcoming can be overcome by exploring a large Q-range, from the low Q-limit to the VDOS limit, especially where the spectral shape varies with momentum transfer due to -though relaxed -selection rules. Thus, additional constraints beyond the VDOS are provided for the lattice dynamics modeling [21,29].…”

“…Directional averaging was performed over a 40 Â 40 polar mesh ( 1 = 12 of sphere) for momentum transfers inside the Brillouin zone centered around (000); the mesh size was progressively increased with Q. While the introduction of an orientation distribution function to the sampling procedure is straightforward [21], it was unnecessary in this particular case.…”

Lattice dynamics of stishovite from powder inelastic X‐ray scattering

“…Therefore, additional constraints are provided for lattice dynamics. It was shown that a combination of force field model calculations and IXS can provide full lattice dynamics, including phonon dispersion curves, from powder measurements [Fischer et al, 2009]. However, the use of force fields is rather problematic, as these have a very limited transferability.…”

“…Here we show that a combination of parameter-free quantum mechanical calculations and IXS can be used to recover the lattice dynamics from polycrystals. The proposed methodology follows the approach of Fischer et al [2009], and consists of recording IXS spectra over a large Q region, and interpret them with model spectra calculated using a lattice dynamics model and the orientation distribution function (ODF) of the polycrystal.…”

Introduction to the theory of lattice dynamics

“…These multi-dimensional maps are sufficiently rich in detail that increasingly we need matching calculations to enable interpretation. We have developed methods to compute the neutron scattering maps taking account of resolution and course corrections for multiphonon and multiple scattering; similar methods have also been developed for inelastic x-ray scattering [32]. These methods are able to interpret experiments performed using single crystals, and also using polycrystalline samples.…”