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Title: Evidence for structural crossover in the supercritical state

The state of matter above the critical point is terra incognita, and is loosely discussed as a physically homogeneous flowing state where no differences can be made between a liquid and a gas and where properties undergo no marked or distinct changes with pressure and temperature. In particular, the structure of supercritical state is currently viewed to be the same everywhere on the phase diagram, and to change only gradually and in a featureless way while moving along any temperature and pressure path above the critical point. Here, we demonstrate that this is not the case, but that there is a well-defined structural crossover instead. Evidenced by the qualitative changes of distribution functions of interatomic distances and angles, the crossover demarcates liquid-like and gas-like configurations and the presence of medium-range structural correlations. Importantly, the discovered structural crossover is closely related to both dynamic and thermodynamic crossovers operating in the supercritical state, providing new unexpected fundamental interlinks between the supercritical structure, dynamics, and thermodynamics.
Authors:
 [1] ; ;  [2] ;  [3] ;  [2] ;  [4]
  1. Baker Laboratory, Cornell University, Ithaca, New York 14853-1301 (United States)
  2. Institute for High Pressure Physics, RAS 142190, Troitsk, Moscow Region (Russian Federation)
  3. (Russian Federation)
  4. School of Physics and Astronomy, Queen Mary University of London, Mile End Road, London E1 4NS, UK and South East Physics Network (SEPnet) (United Kingdom)
Publication Date:
OSTI Identifier:
22253765
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Chemical Physics; Journal Volume: 139; Journal Issue: 23; Other Information: (c) 2013 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; DISTRIBUTION FUNCTIONS; INTERATOMIC DISTANCES; LIQUIDS; PHASE DIAGRAMS; SUPERCRITICAL STATE; THERMODYNAMICS