Structural information extracted from the diffraction of XFEL fs-pulses in a crystal

TL;DR

This paper proposes a theoretical method to extract additional structural information from XFEL diffraction data, improving phase retrieval for determining atomic positions in crystals.

Contribution

It introduces a simulation-based approach to determine absolute structure factors and phases for multi-atomic crystals using XFEL pulse variations.

Findings

Evaluation of diffraction intensities yields atomic structure factors.

Method enables determination of relative phases between atoms.

Accuracy depends on fluctuations of atomic scattering factors.

Abstract

We present a theoretical justification for a method of extracting of supplementary information for the phase retrieval procedure taken from diffraction of fs-pulses from X-ray Free Electron Laser facilities. The approach is based on numerical simulation of the dynamics of the electron density in the crystal composed of different atoms in the unit cell, namely a bi-atomic crystal containing heavy and light atoms. It is shown that evaluation of diffraction intensities measured by means of different values of XFEL pulse parameters enables to find absolute values of structure factors for both types of atoms and their relative phase. The accuracy of structural information is discussed in terms of fluctuations of the evaluated atomic scattering factors. Our approach could be important for improvement of phase retrieval methods with respect to a more efficient determination of atomic positions within the unit cell of macromolecules.