Local order in natural sanidine disentangled via single crystal diffuse scattering

@misc{wiggers2026local,
  title = {{Local order in natural sanidine disentangled via single crystal diffuse scattering}},
  author = {Christin Wiggers and Daniel A. Chaney and Ella M. Schmidt},
  howpublished = {arXiv},
  year = {2026},
  month = sep,
  doi = {10.48550/arxiv.2609.29899},
  eprint = {2609.29899},
  archivePrefix = {arXiv},
  url = {https://arxiv.org/abs/2609.29899},
}

TY  - UNPB
TI  - Local order in natural sanidine disentangled via single crystal diffuse scattering
AU  - Christin Wiggers
AU  - Daniel A. Chaney
AU  - Ella M. Schmidt
PY  - 2026
DA  - 2026/09/24
PB  - arXiv
DO  - 10.48550/arxiv.2609.29899
UR  - https://arxiv.org/abs/2609.29899
AB  - Natural sanidine commonly preserves metastable chemical disorder at ambient conditions, but the local structural correlations associated with this disorder remain poorly understood due to a reliance on average-structure analysis alone. Here, we investigate single-crystal diffuse scattering in a natural sanidine from Drachenfels, Germany, with consistent observations across additional samples from Laacher See, Germany, and Vesuvio, Italy. The diffraction data reveal pronounced anisotropic diffuse features, including characteristic bowtie-like intensity distributions in reciprocal space. To resolve the origin of these features, we combine three-dimensional difference pair distribution function (3D-ΔPDF) analysis with force-field calculations and Monte Carlo modelling. The 3D-ΔPDF shows correlated deviations from the average structure and indicates a strong coupling between occupational and displacive disorder. Force-field calculations demonstrate that the aluminosilicate framework responds strongly to the local alkali occupancy, with the largest structural variation occurring along the a direction. Guided by these observations, we construct a disorder model in which K/Na occupational short-range order is combined with chemically constrained Al/Si distributions and local framework relaxations. The model reproduces the main experimental diffuse-scattering features and shows that the bowtie-like diffuse scattering arises from correlated framework distortions driven primarily by local K/Na order.
ER  -