Monte Carlo simulations of phosphate polyhedron connectivity in glasses

Monte Carlo (MC) simulations of phosphate tetrahedron connectivity distribu tions in alkali and alkaline earth phosphate glasses are reported. By utili zing a discrete bond model, the distribution of next-nearest neighbor conne ctivities between phosphate polyhedron for random, alternating and clusteri ng bonding scenarios was evaluated as a function of the relative bond energ y difference. The simulated distributions are compared to experimentally ob served connectivities reported for solid-state two-dimensional (2D) exchang e and double-quantum (2Q) nuclear magnetic resonance (NMR) experiments of p hosphate glasses. These MC simulations demonstrate that the polyhedron conn ectivity is best described by a random distribution in lithium phosphate an d calcium phosphate glasses. (C) 2000 Elsevier Science B.V. All rights rese rved.