“Pressure-induced structural crossover in liquid GeI 4 ” SEMINAR ANNOUNCEMENT

The similarity in the shape of the melting curve of GeI 4 to that of
SnI 4 prompted us to investigate the existence of a liquid—liquid
transition as observed in liquid SnI 4 . Because the slope of the
melting curve of GeI 4 abruptly changes at around 3 GPa, close
examination using in situ synchrotron x-ray diffraction
measurements was conducted at around 3 GPa. The reduced radial
distribution functions of the high- and low-pressure liquid states of
GeI 4 were found to share the same feature inherent in the high-
pressure and low-pressure radial distribution functions of liquid
SnI 4 . This feature allows us to introduce local order parameters that
we may use to describe the structural variation. Unlike the
transition in liquid SnI 4 , the transition from the low-pressure to the
high-pressure structure seems sluggish. We speculate that the liquid–
liquid critical point of GeI 4 is no longer a thermodynamically stable
state and is slightly located below the melting curve. The behavior
of the local-order parameters implies a metastable extension of the
liquid–liquid phase boundary with a negative slope.