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

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.