Crystal structure solution from experimentally determined atomic pair distribution functions

TL;DR

This paper extends the Liga algorithm to determine crystal structures from atomic pair distribution functions, successfully solving 14 out of 16 test cases involving complex periodic structures.

Contribution

It introduces a two-step method combining the Liga algorithm with atomic radius overlap minimization for structure solution from PDF data.

Findings

Successful solution for 14 of 16 test samples

Effective handling of complex super cells

Discussion of algorithm limitations and improvements

Abstract

The paper describes an extension of the Liga algorithm for structure solution from atomic pair distribution function (PDF), to handle periodic crystal structures with multiple elements in the unit cell. The procedure is performed in 2 separate steps - at first the Liga algorithm is used to find unit cell sites consistent with pair distances extracted from the experimental PDF. In the second step the assignment of atom species over cell sites is solved by minimizing the overlap of their empirical atomic radii. The procedure has been demonstrated on synchrotron x-ray PDF data from 16 test samples. The structure solution was successful for 14 samples including cases with enlarged super cells. The algorithm success rate and the reasons for failed cases are discussed together with enhancements that should improve its convergence and usability.