The molecular dynamics study of lithium ion conduction in phosphate glasses and the role of non-bridging oxygen

Molecular dynamics (MD) simulation of lithium phosphate (Li2O-P2O5) glasses with varying Li2O content has been carried out. Two different P-O distance s corresponding to phosphorus coordination with bridging oxygen (BO) and no n-bridging oxygen (NBO) were identified in the simulated glasses. NBO-BO in terconversion or bond switching was noted, which results in a dynamic equil ibration of the tetrahedral phosphate units (P-n, n = 1,3 indicates the num ber of bridging oxygen atoms in the coordination of phosphorus). The NBO-BO bond switching is mildly activated with an effective activation barrier of 0.03-0.05 eV. Lithium ion jumps do not appear to be strongly coupled to bo nd switching. But the number of Li+ ions coordinated to an optimum number o f NBOs and the number of Li+ ions jumping out of their sites appear to be c orrelated. Detailed analysis was made of the dynamics of P-n species and ne w insights have been obtained regarding ion migration in network-modified p hosphate glasses.