Pressure-induced structural change in liquid GeI.

The similarity in the shape of the melting curve of GeI to that of SnI suggests that a liquid-liquid transition as observed in liquid SnI is also expected to occur in liquid GeI. Because the slope of the melting curve of GeI abruptly changes at around 3 GPa, in situ synchrotron diffraction measurements were conducted to examine closely the structural changes upon compression at around 3 GPa. The reduced radial distribution functions of the high- and low-pressure liquid states of GeI share the same feature inherent in the high-pressure (high-density) and low-pressure (low-density) radial distribution functions of liquid SnI.

Communication: probable scenario of the liquid-liquid phase transition of SnI4.

We have shown from in situ synchrotron x-ray diffraction measurements that there are two thermodynamically stable liquid forms of SnI(4), depending on the pressure. Based on the liquid-liquid critical point scenario, our recent measurements suggest that the second critical point, if it exists, may be located in a region close to the point at which the melting curve of the crystalline phase abruptly breaks. This region is, unlike that of water, experimentally accessible with relative ease.

Polyamorphism in tin tetraiodide.

The discovery of a first-order phase transition in fluid phosphorus aroused renewed interest in polyamorphism in liquids with a locally tetrahedral molecular structure. We have performed in situ synchrotron x-ray diffraction measurements on tin tetraiodide, which consists of SnI(4) tetrahedral molecules at ambient pressure, and established that the liquid forms existing above and below 1.5 GPa, where the slope of the melting curve of the solid phase changes abruptly, have different structures.