Quantifying orientational ordering in tetrahedrally-bonded liquids

Network-forming melts such as water, silica, Si, Ge, C, GeO2 or BeF2 exhibit distinctive local tetrahedral symmetry which is thought to be at the origin of known thermodynamic anomalies. Recent simulation results emphasize the important role of local ordering in the second co-ordination shell in determining the origin of the anomalies referred to. Molten BeF2 represents a close analogue to silica which because of the weaker Be–F interaction, shows both melting (1076 K) and glass-transition (580 K) points at significantly lower temperatures than silica and thus appears as an optimal candidate to check the accuracy of the computer simulation predictions. Here we propose to conduct a series of measurements to determine the structural order of BeF2 to check the accuracy of published simulation results for the material by means of a direct comparison of the total radial distributions.