BzScope: an absolute cross section calculator for neutron-phonon scattering

TL;DR

BzScope is a Python tool that accurately calculates neutron-phonon scattering cross sections in crystalline powders, improving upon traditional methods and integrating with Monte Carlo simulations for condensed matter studies.

Contribution

It introduces an efficient integral method for calculating absolute cross sections, supporting high-order scatterings and integration with NCrystal for enhanced neutron scattering simulations.

Findings

Validated against NCrystal with good agreement for cubic Ni

Improved accuracy for low-symmetry NiP2 over NCrystal

Confirmed reliability through benchmarks with LiH and Be

Abstract

BzScope is a Python package designed for efficiently calculating absolute cross sections of neutron-phonon inelastic scattering for crystalline powders in large phase spaces, addressing the limitations of traditional histogramming techniques in reproducing sharp structures and ensuring convergence. The package employs an adapted integral method and supports calculations of single- and two-phonon scattering functions in ideal crystalline powders, with numerical robustness up to a momentum transfer of 100 Ang^-1. Higher order scatterings up to several hundred orders are calculated by incoherent approximation in a well-established thermal neutron scattering physics package, NCrystal. In addition, a NCrystal plugin is made available for NCrystal-enabled Monte Carlo packages, facilitating direct comparison between the new physics and experimental data. Validation against NCrystal demonstrates good agreement in incoherent scattering for cubic systems Ni. In addition, it shows improved accuracy for low-symmetry materials $NiP_2$ by avoiding the isotropic atomic displacement approximations in NCrystal. Benchmarks the experimental differential cross section of LiH and total cross section of Be confirm its reliability. BzScope integrates with NCrystal via a plugin and therefore can be directly used in any NCrystal-enabled Monte Carlo package. This tool enhances the efficiency and accuracy of neutron scattering simulations, advancing the study of condensed matter dynamics.