A continuous random network approach to the structure of vitreous boron trioxide

Abstract

Two models of a three-fold coordinated continuous random network (C.R.N.), originally constructed to simulate the structure of amorphous arsenic (Greaves and Davis 1974), have been converted by means of certain computer procedures into plausible structures of vitreous boron trioxide, B₂O₃.

Using the original coordinates of the arsenic networks as a basis, oxygen sites were positioned at the midpoint of each arsenic bond and boron sites were located at the centre of each triangle, thereby forming interconnected planar BO₃ units. Various structural parameters of the resulting models have been calculated. including radial distribution functions (RDFs), both total and partial, and bond angle distributions. The calculated RDF shows very reasonable agreement with experimental curves deduced from X-ray diffraction work, and reproduces satisfactorily the peaks that have previously been ascribed to six-membered boroxol rings. This is significant since the present model contains no boroxol rings whatsoever.