The ring structure of boron trioxide glass

A new experiment, sensitive to the dihedral angle distribution of neighboring structural units, was applied to boron trioxide glass. The experiment consisted of correlating the NMR frequencies of neighboring boron nuclei. The frequencies are identical if the boron oxide polyhedra containing the two borons are co-planar, as found in ring systems, but differ for non-co-planar geometries. Through the rate of growth of signal intensity arising from the non-co-planar case, as compared to that obtained in a boron trioxide crystal of known structure, the fraction of boron contained in rings in the glass was determined to be 0.70±0.08.