Structural studies on fluid sulfur at high temperatures and high pressures: II. Molecular structure obtained by ab initio molecular dynamics simulations

Abstract An ab initio molecular-dynamics simulation has been carried out to investigate structure of fluid sulfur at 1323 K, a supercritical region. The simulated structure factor agrees well with that experimentally obtained. We found that various kinds of sulfur molecules are formed and a bond at the end of a chain molecule is shorter than that at the inside of the chain. In particular, a S4 chain molecule exhibits approximately 0.3 A difference between them. This result explains the results obtained by x-ray diffraction [Inui et al., J. Phys.: Conf. Ser. 98,012,008 (2008)], why the average bond length is almost constant although the coordination number decreases to 1.0, corresponding to a S2 molecule with a double bond, at low densities.