NCrystal plugin CrysXT

Combined crystalline extinction and texture correction plugin for NCrystal, based on ncplugin-CrysExtn and ncplugin-CrysText. Please refer to those repositories for full model descriptions and parameter details. Only the Sabine (uncorr/corr) and Becker & Coppens (BC_pure, BC_mix, BC_mod) extinction models are supported.

BC models support an optional rec= flag selecting the y(x,θ) recipe: cls (BC1974 classic formula, Becker, P. J. & Coppens, P. (1974). Acta Cryst. A30, 129-147), std (BC2025 standard precision, default), or lux (BC2025 luxury precision). Refs: T. Kittelmann et al., Acta Cryst. (2026). A82, 163-178, https://doi.org/10.1107/S2053273326001245; Thomas Kittelmann. (2026). tkittel/bc-extinction-paper: Supporting material for BC extinction recipe updates v1.0.1 (v1.0.1). Zenodo. https://doi.org/10.5281/zenodo.18493059

Installation

Create a conda environment, install NCrystal via conda install ncrystal, then:

pip install "git+https://github.com/dddijulio/ncplugin-CrysXT"

Syntax

Append a @CUSTOM_CRYSXT section to any .ncmat file using the Extinction and/or Texture keywords. Both are optional but at least one must be present.

@CUSTOM_CRYSXT
  Extinction Sabine_uncorr 30000 1000 100000 rect
  Texture 1 1 1 0.5 0.5
  Texture 1 1 1 0.5 0.5

@CUSTOM_CRYSXT
  Extinction BC_mix 30000 0.001 100000 Gauss rec=lux

• Extinction <model> <l[Å]> <g[1/rad]> <L[Å]> [dist] [rec=cls|std|lux] — see ncplugin-CrysExtn for parameter details. Sabine_corr takes no dist; Sabine_uncorr uses rect/tri; BC models use Gauss/Lorentz/Fresnel. The optional rec= flag (BC models only, default std) selects the extinction recipe: cls = BC1974 classic formula, std = BC2025 standard precision, lux = BC2025 luxury precision.
• Texture <px> <py> <pz> <R> <f> — exactly two lines required, with f1 + f2 = 1. See ncplugin-CrysText for details on the modified March-Dollase model.

Note

This plugin is intended for cross-section calculations only and not for use in Monte Carlo simulations.