Thermodynamic behaviour of supercritical matter.

  title={Thermodynamic behaviour of supercritical matter.},
  author={Dima Bolmatov and Vadim V. Brazhkin and Kostya Trachenko},
  journal={Nature communications},
Since their discovery in 1822, supercritical fluids have been of enduring interest and have started to be deployed in many important applications. Theoretical understanding of the supercritical state is lacking and is seen to limit further industrial deployment. Here we study thermodynamic properties of the supercritical state and discover that specific heat shows a crossover between two different regimes, an unexpected result in view of currently perceived homogeneity of supercritical state in… 
Thermodynamic heterogeneity and crossover in the supercritical state of matter.
This work performs extensive molecular dynamics simulations in a wide temperature range and finds that a deeply supercritical state is thermodynamically heterogeneous, as witnessed by different temperature dependence of energy, heat capacity and its derivatives at low and high temperature.
The Frenkel Line: a direct experimental evidence for the new thermodynamic boundary
Structural crossovers are observed for the first time in a deeply supercritical sample through diffraction measurements in a diamond anvil cell and a new thermodynamic boundary is discovered on the pressure-temperature diagram.
Structural behavior of supercritical fluids under confinement.
The heterogeneity across the Frenkel line, found to be present both in bulk and confined systems, might cause the breakdown of the universal scaling between structure and dynamics of fluids necessitating the determination of a unique relationship between them.
Structural Evolution of Supercritical CO2 across the Frenkel Line.
Structural properties of the supercritical carbon dioxide are studied and the existence of persistent medium-range order correlations are discovered, which make super critical carbon dioxide nonuniform and heterogeneous on an intermediate length scale are discovered.
Evidence for structural crossover in the supercritical state.
It is demonstrated that there is a well-defined structural crossover between the supercritical structure, dynamics, and thermodynamics, and that this crossover demarcates liquid-like and gas-like configurations and the presence of medium-range structural correlations.
Crossover of collective modes and positive sound dispersion in supercritical state.
It is found that the supercritical system sustains propagating solid-like transverse modes below the Frenkel line but not above where there is one longitudinal mode only.
The nature of collective excitations and their crossover at extreme supercritical conditions
Direct evidence is presented for propagating solid-like longitudinal phonon-like excitations with wavelengths extending to interatomic separations deep in the supercritical state at temperatures up to 3,300 times the critical temperature.


Liquidlike behavior of supercritical fluids.
The extrapolation of the liquid-vapor-coexistence line in the (P/Pc, T/Tc) plane is identified as the relevant edge between liquidlike and gaslike dynamics, and points to the existence of a connection between structural modifications and transport properties in dense fluids.
Supercritical fluids : fundamentals and applications
Fluids in the approximate range of temperature and pressure 1 to 1.1 and 1 to 2, respectively (referred to critical conditions) are commonly called supercritical. The thermophysical properties in the
Microscopic relaxation in supercritical and liquid neon
The high frequency behavior of the dynamic structure factor, S(Q,ω), of liquid and supercritical neon is investigated by inelastic x-ray scattering at different temperatures and pressure. The
Thermodynamic signature of growing amorphous order in glass-forming liquids
That the dynamical properties of a glass-forming liquid at high temperature are different from behaviour in the supercooled state has already been established. Numerical simulations now suggest that
The Widom line as the crossover between liquid-like and gas-like behaviour in supercritical fluids
According to textbook definitions 1 , there exists no physical observable able to distinguish a liquid from a gas beyond the critical point, and hence only a single fluid phase is defined. There are,
Entropy-driven liquid–liquid separation in supercooled water
A thermodynamic model based on the hypothesis that the anomalous properties of supercooled water may be caused by a critical point that terminates a line of liquid–liquid separation of lower-density and higher-density water is presented.
The phonon theory of liquid thermodynamics
A phonon theory of liquids is developed where the perceived difficulty is that interactions in a liquid are both strong and system-specific, implying that the energy strongly depends on the liquid type and that liquid energy can not be calculated in general form.
Two liquid states of matter: a dynamic line on a phase diagram.
The new dynamic line is universal: It separates two liquid states at arbitrarily high pressure and temperature and exists in systems where liquid-gas transition and the critical point are absent altogether.
Viscosity of glass-forming liquids
This work presents a model offering an improved description of the viscosity–temperature relationship for both inorganic and organic liquids using the same number of parameters as VFT and AM, and casts doubt on the existence of a Kauzmann entropy catastrophe and associated ideal glass transition.
Scaling behavior in the dynamics of a supercooled Lennard-Jones mixture
SummaryWe present the results of a large-scale molecular-dynamics computer simulation of a binary, supercooled Lennard-Jones fluid. At low temperatures and intermediate times the time dependence of