A neutron diffraction, isotopic substitution study of the structure of Li2O•2SiO2 glass

The structure of Li2O . 2SiO(2) glass has been studied in detail by neutron diffraction with isotopic substitution of Li, The first Si-O and O-O distances are 0.163 +/- 0.001 Ind 0.266 +/- 0.001 nm, respectively. Li is found in a relatively well-defined tetrahedral site, with 3.2 +/- 0.2 oxygen atoms at 0.197 +/- 0.001 nm and a further 0.8 +/- 0.5 in a broad rail extending to about 0.22, The Li-Li first neighbour distance in a silicate glass has been measured directly, for the first time, and the value of 0.310 +/- 0.002 nm yields strong evidence for a non-random distribution of the Li ions in the glass. The short- and medium-range structure exhibit considerable similarity to those of crystalline (c-) lithium disilicate. (C) 1998 Elsevier Science B.V. All rights reserved.