In situ observation of a first-order liquid-liquid transition in phosphorus

Katayama, Yoshinori

Recently, we have found a sharp pressure-induced structural change between two characteristic structures of liquid phosphorus by an in-situ high-temperature high-presusre x-ray diffraction method using a JAERI beamline, BL14B1, at SPring-8. Our observations --- existence of molecular and polymeric liquids, sharp and reversible change between them and coexistence of two structures during the change --- strongly support that the structural change is a first-order liquid-liquid phase transition. It has been confirmed that the two liquid phases have different densities by a determination of melting curve by x-ray diffraction and by a density measurement by means of x-ray absorption. The structure of liquid P under high pressure resembles that of liquid arsenic.