Keynote
THERMODYNAMIC AND DYNAMICAL PHASE TRANSFORMATIONS IN LIQUIDS AT SUPERCRITICAL PRESSURES

It was established experimentally that in the vicinity of the melting curves, including the pressures and temperatures above critical, all fluids have some short and intermediate range order and their excitation spectrum contains high-frequency shear waves. Both smooth and sharp first-order phase transformations with the changes of the liquids structure and properties are possible under high pressures. However, at sufficiently high temperatures, all liquids must lose their identity and transform into unstructured dense gas state, in which only longitudinal waves propagate. The theoretical and experimental evidences for the existence of boundary between "solid-like" melt and dense gas at supercritical pressures are discussed.