The Complemented System Approach: A Novel Method for Calculating the X-ray Scattering from Computer Simulations

TL;DR

This paper introduces a new method for calculating X-ray scattering from simulated systems that overcomes finite size limitations by complementing missing surroundings, providing accurate, artifact-free results directly from particle configurations.

Contribution

The paper presents a novel complemented system approach based on the Rayleigh-Debye-Gans approximation, enabling direct calculation of X-ray scattering without intermediate steps.

Findings

The method produces scattering curves free of truncation artifacts.

It maintains good behavior down to the lowest q-values.

The approach is computationally efficient compared to existing methods.

Abstract

In this paper, we review the main problem concerning the calculation of X-ray scattering of simulated model systems, namely their finite size. A novel method based on the Rayleigh-Debye-Gans approximation was derived, which allows sidestepping this issue by complementing the missing surroundings of each particle with an average image of the system. The method was designed to operate directly on particle configurations without an intermediate step (e.g., calculation of pair distribution functions): in this way, all information contained in the configurations was preserved. A comparison of the results against those of other known methods showed that the new method combined several favourable properties: an arbitrary q-scale, scattering curves free of truncation artifacts and good behaviour down to the theoretical lower limit of the q-scale. A test of computational efficiency was also performed to establish a relative scale between the speeds of all known methods: the reciprocal lattice approach, the brute force method, the Fourier transform approach and the newly presented complemented system approach.