Structural study of lithium phosphate glasses by X-ray RDF and computer simulations

The structures of xLi2O–(1−x)P2O5 glasses with x=0.10, 0.20 and 0.30 have been examined using X-ray radial distribution functions. The composition range x=0.10–0.75 also has been studied by molecular dynamics simulations. MD configurations were analyzed using graph theory techniques. The experimental glass transition temperature reaches a minimum at 20mol% of Li2O and the simulated glass has a minimum Tg at 23mol% of Li2O. This minimum in Tg has been explained by studying the changes in the environment of Li, P and O with Li2O composition and connectivities among the PO4 groups mediated by lithium existing in the network. X-ray RDF studies agree with the MD simulation results. Dynamic parameters of interest to structure-transport studies, namely mean square displacement and velocity autocorrelation function obtained from the MD simulations, identify Li+ as the mobile ion contributing to ionic conductivity.