Pressure-induced structural change in liquid Ge_0.15Te _0.85 alloy

X-ray diffraction has been measured up to 2.4 GPa for liquid Ge _0.15Te_0.85 alloy using synchrotron radiations. Static structure factor S(Q) and pair distribution function g(r) were obtained. At 0.5 GPa, S(Q) shows different temperature dependence below and above 700 K. With increasing temperature above 700 K the increasing rate of the height ratio between the first and second peaks in S(Q) becomes moderated. This finding suggests a temperature-induced structural transformation occurs at 700K. At 1.8 GPa and 2.4 GPa such anomalous behaviour was not observed in the temperature region from the melting temperature to 850 K. The boundary between the low-temperature and the high-temperature phases has a negative slope. The Clausius-Clapeyron equation suggests the high-temperature phase has larger entropy than the low-temperature one.