The local structure of Fe in Li(Al, Fe)Si2O6 glasses from molecular dynamics simulations

As an impurity or an additive, the introduction of Fe to alumino-silicate glasses could lead to changes in structure and physical properties. In this study, the structure and physical properties of LiAl1-xFexSi2O6 (x = 0, 0.17, 0.5, 0.83 and 1) glasses were analyzed using molecular dynamics simulations. The results show that Fe3+ is mainly four-coordinated and the FeO4 tetrahedron is more distorted than the SiO4 and AlO4 tetrahedra. In addition to four-coordinated Fe3+, a minor amount of 5-coordinated Fe3+ (about 6% of total Fe3+), irrespective of the Fe concentration, was, present. The concentration of 4-coordinated Fe3+ decreases but of 5-coordinated Fe3+ increases with increasing temperature, especially at temperatures above T-g. Both 4-coordinated and 5-coordinated Fe3+ show a marked tendency to aggregate, centered around the network modifier Li+, but with a random distribution around the network formers Si4+ and Al3+. In the clusters, FeO5 polyhedra mainly share edges, while FeO4 tetrahedra share corners with each other. The simulations show that, with increasing Fe concentration, the volume and density of the glass increase but T-g shows a contrary change. (C) 2016 Published by Elsevier B.V.