AsS melt under pressure; One substance, three liquids

Brazhkin, V. V.*; Katayama, Yoshinori; Kondrin, M. V.*; Hattori, Takanori   ; Lyapin, A. G.*; Saito, Hiroyuki

An high-temperature high-pressure X-ray diffraction, resistivity measurements, and quenching from melt were performed on liquid chalcogenide AsS. The obtained data provide direct evidence for the existence three forms in the melt under compression: one is a moderate viscosity molecular liquid, the second one is a high-viscosity nonmetallic polymerized liquid and the third one is a low-viscosity metallic liquid. The two transformations occur at P 1.6-2.2 GPa and at P 4.6-4.8 GPa. Upon rapid cooling, molecular and metallic liquids crystallize to normal and high-pressure phases, respectively, while a polymerized liquid is easily quenched to a new AsS glass. General aspects of multiple phase transitions in liquid AsS, including relations to the phase diagram of the respective crystalline, are discussed.