Structure of Vitreous B2O3·⅓H2O

A boron oxide glass containing 25 mole percent water, corresponding to the formula B2O3·⅓H2O, has been prepared and its structure studied. Diffractometric x-ray scattering measurements have been made for both vitreous B2O3·⅓H2O and vitreous B2O3, and from these measurements radial distribution functions have been computed. Examination of the atomic distribution function of B2O3·⅓H2O and comparison of the electronic distribution functions of B2O3·⅓H2O and B2O3 indicate that the fundamental triangular coordination of vitreous B2O3 is retained in B2O3·⅓H2O, but the network of the latter is somewhat looser than that of the former. It is suggested that while most of the oxygen atoms are shared between boron atoms, some of the oxygens are present in hydroxyl groups or O–H–O hydrogen bonds. The possibility that a small fraction of the boron atoms are coordinated by four oxygen atoms is not completely excluded.