Structure of covalently bonded glass-forming melts: A full partial-structure-factor analysis of liquid GeSe2

The first full partial-structure-factor analysis of molten GeSe2 is made using the method of isotopic substitution in neutron diffraction. It is shown that the melt comprises roughly equal numbers of edge- and corner-sharing tetrahedra which give rise to a highly connected or network liquid. Concentration fluctuations extend over distances characteristic of the intermediate-range order, contrary to the results obtained from recently developed effective potentials for covalently bonded glass-forming melts. The problem as to whether or not GeSe2 forms a chemically ordered continuous random network is examined.