P-31 solid-state NMR studies of the short-range order in phosphorus-selenium glasses

The local structure of P-rich and Se-rich phosphorus-selenium glasses was studied using high-resolution P-31 solid-state MAS NMR. Two-dimensional P-31 homonuclear through-bond correlation MAS experiments and 2D homonuclear J-resolved MAS measurements were performed at high spinning frequency to probe P-P and P-Se-P connectivities between the different P sites for the compounds in two glass-forming regions, P2.5Se97.5-P50Se50 and P67Se33-P84Se16. Amorphous phosphorus and crystalline alpha-P4Se3 and beta-P4Se3 were also studied as reference materials. Glasses from the Se-rich region contain mainly three-and four-coordinated P sites linked together by Se-n chains, whereas P-rich glasses contain a mixture of P4Se3 molecular units and possibly other structural units embedded in a red-phosphorus-like polymeric network.