Modeling diffuse scattering using first-principles based methods

Anh Ngo, Justin M. Wozniak, Jonathan Morris, Stephan Rosenkranz,
Raymond Osborn, and Peter Zapol
                  
Proc. Materials Research Society Fall Meeting 2015

Disorder in crystalline materials is directly linked to their
functionalities in many applications such as advanced battery
electrodes and solid fuel cell electrolytes. First principles-based
methods are capable of calculating the energetic preference of
specific defect arrangements in a material and thus providing unbiased
models that can be combined with experimental diffuse scattering data
to derive quantitative correlations in defect distributions. A
combination of first-principles calculations, the cluster expansion
method and kinetic Monte Carlo is demonstrated to produce defect
correlations in mullite Al2[Al2x+2Si2-2x]O10-x, a prototypical
material for diffuse scattering, in agreement with experimental
results. The modeling includes correlations in both the disordered
oxygen sublattice and the cation sublattice. This approach will enable
the integration of ab initio methods with x-ray diffuse scattering
measurements over large volumes of reciprocal space, using Swift/T, a
dataflow language for scientific computing on HPC systems, to
accelerate analysis and model refinement.