Structure and dynamics of liquid sulphur

First-principles molecular dynamics calculations based on density-functional theory have been used to predict the structure, vibrational spectrum, and dynamics of liquid sulphur over a wide temperature range. The calculated structure factor is in excellent agreement with that derived from neutron diffraction experiments. At low temperature, the liquid structure is found to consist primarily of Sg rings. The theoretical calculations provide important structural information that may not be possible to extract from experiment. The structure at high temperatures and/or after photoexcitation is found to consist of chains of varying lengths resulting from the breakup of the S-8 rings. Upon quenching, longer helical chains and cross linkages an observed indicating the initial stage of polymerization. The self-diffusion constant of liquid sulphur first increases slowly reflecting the interpenetrating chains and rings but increases rapidly as the rings break up into smaller chains. [S0163-1829(99)02401-7].