Quantitative determination of the structural units in phosphorus-selenium glasses byP31dipolar and magic-angle-spinning NMR spectroscopy

The detailed quantitative speciation of phosphorus and selenium microstructures in phosphorus-selenium glasses is derived from combined ${}_{}{}^{31}{}_{}{}^{}\mathrm{P}$ spin-echo and magic-angle-spinning NMR experiments. The results illustrate that the structure of these glasses differs from the chemically ordered or clustered structures previously proposed, but are also at variance with a completely random distribution. There is a distinct preference for the formation of P-Se versus P-P and Se-Se bonds, which can be quantified from the present experiments. The site speciation shows no dramatic changes near the composition (40 at.% P) corresponding to the rigidity percolation threshold.