Reverse Monte Carlo and Rietveld modelling of BaMn(Fe,V)F7 glass structures from neutron data

TL;DR

This study models the structure of BaMn(Fe,V)F7 glasses using neutron data, applying RMC and Rietveld methods, revealing that multiple models fit the data similarly, indicating complex short-range order.

Contribution

It demonstrates the application of RMC and Rietveld methods to fluoride glasses, showing the difficulty in distinguishing structures with limited interference functions.

Findings

Best fit obtained with crystalline BaMnGaF7 structure-type

Small difference in fit quality among multiple models

Average short and medium range order similar across models

Abstract

Fluoride glasses BaMnMF7 (M = Fe, V, assuming isomorphous replacement) have been structurally modelled. The neutron patterns were simulated by the reverse Monte Carlo (RMC) and the Rietveld for disordered materials (RDM) methods. The best fit is obtained from one of the seven tested crystalline models : the BaMnGaF7 structure-type in which the glasses crystallize. However, by RMC applied to enlarged RDM models, the difference between the best and the worst fit is quite small (DRp ~ 0.5%), suggesting that two interference functions are not enough for the characterization of such multicomponent glasses, or that the average short and medium range order is similar in the seven models in spite of strong differences in the polyhedra linkage.