BOROXOL GROUPS IN VITREOUS BORON-OXIDE - NEW EVIDENCE FROM NEUTRON-DIFFRACTION AND INELASTIC NEUTRON-SCATTERING STUDIES

Although the nuclear magnetic resonance (NMR) and neutron diffraction evidence for the majority of the boron atoms in vitreous boron oxide b eing involved in boroxol groups would seem to be irrefutable, neverthe less several recent papers have challenged this conclusion. The presen t paper, therefore, examines these claims in the light of neutron diff raction data, with much greater accuracy than those reported previousl y, and of neutron inelastic scattering results, optimised to give the highest possible energy transfer resolution in the region of the borox ol ring breathing mode. A fit to the interference function, Qi(Q), ind icates that the fraction, f, of boron atoms in boroxol groups is 0.80 +/- 0.05, while the neutron weighted density of states exhibits a well resolved boroxol ring breathing mode of similar magnitude to the theo retical prediction for a structural model with f = 0.75. Both results confirm the conclusion of the earlier NMR and neutron studies.