Abstract The structures of xLi 2O–(1 − x)P 2O 5 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 20 mol% of Li 2O and the simulated glass has a minimum T g at 23 mol% of Li 2O. This minimum in T g has been explained by studying the changes in the environment of Li, P and O with Li 2O composition and connectivities among the PO 4 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.