X-ray diffraction measurements of expanded fluid sulfur up to the supercritical region

Abstract

The structure factor, S(Q), of fluid sulfur was measured up to 1573 K and 30 MPa using synchrotron radiation at SPring-8 in Japan. The pair distribution function, g(r), deduced from S(Q) exhibits the first peak well separated from higher coordination shells in the entire density region from liquid to dense vapour. At 0.6 g cm−3 near the critical density the coordination number of the first peak is one but the bond length remains approximately 2 Å, longer than that of an isolated S2 molecule. These results hint a strong intermolecular interaction between S2 molecules in the dense vapour phase near the critical density in the supercritical region.