INTERMEDIATE RANGE ORDERING IN A NETWORK GLASS

The extent of intermediate range order in a network glass, B2O3, has b een investigated using the reverse Monte Carlo method and reported neu tron diffraction data. The first sharp diffraction peak (FSDP) in the static structure factor, S(Q), which is an experimental signature of i ntermediate range order, is found to be dependent on the size of the c onfiguration, whereas the remaining part of S(Q) is almost unaffected. Correlations in the range 0.4 to 1 nm are shown to be of particular i mportance for the shape of the FSDP. The origin of the FSDP in B2O3 is a weak correlation between neighbouring segments of BO3 triangles sep arated by voids in the structure. This inter-segment correlation produ ces a damped oscillation with a period of about 0.4 nm in the total pa ir correlation function. The quasi-periodicity extends out to about 1. 5 nm, which thereby is the longest structural correlation length of th is glass. (C) 1998 Elsevier Science B.V.