The Frenkel Line: a direct experimental evidence for the new thermodynamic boundary

Supercritical fluids play a significant role in elucidating fundamental aspects of liquid matter under extreme conditions. They have been extensively studied at pressures and temperatures relevant to various industrial applications. However, much less is known about the structural behaviour of supercritical fluids and no structural crossovers have been observed in static compression experiments in any temperature and pressure ranges beyond the critical point. The structure of supercritical state is currently perceived to be uniform everywhere on the pressure-temperature phase diagram, and to change only in a monotonic way even moving around the critical point, not only along isotherms or isobars. Conversely, we observe structural crossovers for the first time in a deeply supercritical sample through diffraction measurements in a diamond anvil cell and discover a new thermodynamic boundary on the pressure-temperature diagram. We explain the existence of these crossovers in the framework of the phonon theory of liquids using molecular dynamics simulations. The obtained results are of prime importance since they imply a global reconsideration of the mere essence of the supercritical phase. Furthermore, this discovery may pave the way to new unexpected applications and to the exploration of exotic behaviour of confined fluids relevant to geo- and planetary sciences.

[1]  T. Schrøder,et al.  Explaining why simple liquids are quasi-universal , 2014, Nature Communications.

[2]  M. Braga,et al.  Calorimetric measurements and first principles to study the (Ag-Li) liquid system , 2015 .

[3]  P. Debenedetti.  Supercritical fluids : fundamentals and applications , 1994 .

[4]  S. Saxena,et al.  Temperature-induced ruby fluorescence shifts up to a pressure of 15 GPa in an externally heated diamond anvil cell , 1999 .

[5]  J. C. Martinez-Garcia,et al.  Nonlinear dielectric effect in supercritical diethyl ether. , 2014, The Journal of chemical physics.

[6]  J. Frankel.  Kinetic theory of liquids , 1946 .

[7]  Y. Cai,et al.  Unified phonon-based approach to the thermodynamics of solid, liquid and gas states , 2015, 1512.07191.

[8]  John C. Mauro,et al.  Viscosity of glass-forming liquids , 2009, Proceedings of the National Academy of Sciences.

[9]  M. G. RUSBRIDGE,et al.  Kinetic Theory , 1969, Nature.

[10]  A phonon thermodynamics approach of gold nanofluids synthesized in solution plasma , 2014 .

[11]  G. Biroli,et al.  Thermodynamic signature of growing amorphous order in glass-forming liquids , 2008, 0805.4427.

[12]  Jean-Pierre Hansen,et al.  Basic Concepts for Simple and Complex Liquids: Curvature and fluctuations , 2003 .

[13]  B. Widom,et al.  Equation of State in the Neighborhood of the Critical Point , 1965 .

[14]  F. Macdougall.  THE EQUATION OF STATE FOR GASES AND LIQUIDS. , 1916 .

[15]  J. Kirkwood.  Statistical Mechanics of Fluid Mixtures , 1935 .

[16]  K. Trachenko,et al.  Helium at elevated pressures: Quantum liquid with non-static shear rigidity , 2013, 1303.2031.

[17]  High-frequency asymptotics of dielectric permittivity in supercooled liquids: Experimental data and conclusions of mode-coupling theory , 2014 .

[18]  Dima Bolmatov,et al.  Revealing the Mechanism of the Viscous-to-Elastic Crossover in Liquids. , 2015, The journal of physical chemistry letters.

[19]  K. Trachenko,et al.  Evidence for structural crossover in the supercritical state. , 2013, The Journal of chemical physics.

[20]  F. Gorelli,et al.  Structural changes in supercritical fluids at high pressures , 2008 .

[21]  V. Giordano,et al.  Fingerprints of order and disorder on the high-frequency dynamics of liquids , 2010, Proceedings of the National Academy of Sciences.

[22]  Yu. D. Fomin,et al.  Two liquid states of matter: a dynamic line on a phase diagram. , 2011, Physical review. E, Statistical, nonlinear, and soft matter physics.

[23]  S. Tauber,et al.  Functional Activity of Plasmid DNA after Entry into the Atmosphere of Earth Investigated by a New Biomarker Stability Assay for Ballistic Spaceflight Experiments , 2014, PloS one.

[24]  Melting Curves of Hydrogen, H2O, Helium and Argon at High Pressure , 1998 .

[25]  B. Militzer,et al.  A multiphase equation of state for carbon addressing high pressures and temperatures , 2013, 1311.4577.

[26]  Neil W. Ashcroft,et al.  Theory of simple classical fluids: Universality in the short-range structure , 1979 .

[27]  P. Debye.  Zur Theorie der spezifischen Wärmen , 1912 .

[28]  G. Ruppeiner,et al.  Thermodynamic $R$-diagrams reveal solid-like fluid states , 2014, 1411.2872.

[29]  D. Haar,et al.  Statistical Physics , 1971, Nature.

[30]  G. Ruocco,et al.  The Widom line as the crossover between liquid-like and gas-like behaviour in supercritical fluids , 2010 .

[31]  Antje Sommer,et al.  Theory Of Simple Liquids , 2016 .

[32]  S. Sinogeikin,et al.  BX90: a new diamond anvil cell design for X-ray diffraction and optical measurements. , 2012, The Review of scientific instruments.

[33]  N. Budisa,et al.  Supercritical Carbon Dioxide and Its Potential as a Life-Sustaining Solvent in a Planetary Environment , 2014, Life.

[34]  Dima Bolmatov,et al.  Thermodynamic behaviour of supercritical matter , 2013, Nature Communications.

[35]  R. G. Wenzel,et al.  Structure Factor and Radial Distribution Function for Liquid Argon at 85 °K , 1973 .

[36]  Y. Rosenfeld.  THE THEORY OF SIMPLE CLASSICAL FLUIDS : UNIVERSALITY IN THE SHORT RANGE STRUCTURE , 1980 .

[37]  M. Gao,et al.  Persistent local order heterogeneity in the supercritical carbon dioxide , 2014 .

[38]  T. Bryk,et al.  Dynamics and Thermodynamics beyond the critical point , 2013, Scientific Reports.

[39]  G. Szamel,et al.  Characterizing dynamic length scales in glass-forming liquids , 2012, Nature Physics.

[40]  Understanding the atomic-level Green-Kubo stress correlation function for a liquid through phonons in a model crystal , 2014 .

[41]  Kostya Trachenko,et al.  Liquid heat capacity in the approach from the solid state: Anharmonic theory , 2011, 1103.4011.

[42]  D. Bolmatov.  II. THE EQUATIONS OF STATE IN THE THEORY OF SIMPLE LIQUIDS , 2009 .

[43]  K. Trachenko,et al.  Dynamic transition of supercritical hydrogen: defining the boundary between interior and atmosphere in gas giants. , 2013, Physical review. E, Statistical, nonlinear, and soft matter physics.

[44]  V. Prakapenka,et al.  DIOPTAS: a program for reduction of two-dimensional X-ray diffraction data and data exploration , 2015 .

[45]  V. V. Brazhkin,et al.  The phonon theory of liquid thermodynamics , 2012, Scientific Reports.

[46]  M. Gao,et al.  Structural Evolution of Supercritical CO2 across the Frenkel Line. , 2014, The journal of physical chemistry letters.

[47]  L. Larini,et al.  Universal scaling between structural relaxation and vibrational dynamics in glass-forming liquids and polymers , 2008 .

[48]  "Liquid-gas" transition in the supercritical region: fundamental changes in the particle dynamics. , 2013, Physical review letters.

[49]  Dima Bolmatov,et al.  Symmetry breaking gives rise to energy spectra of three states of matter , 2013, Scientific Reports.

[50]  K. E. Bett,et al.  Effect of Pressure on the Viscosity of Water , 1965, Nature.

[51]  G. Malenkov.  Argon and water , 2013, Journal of Structural Chemistry.

[52]  David P. Landau,et al.  Phase transitions and critical phenomena , 1989, Computing in Science & Engineering.

[53]  M. Mezouar,et al.  Quantitative structure factor and density measurements of high-pressure fluids in diamond anvil cells by x-ray diffraction: Argon and water , 2002 .

[54]  Martin T. Dove,et al.  Structure and dynamics : an atomic view of materials , 2003 .

[55]  C. Angell.  Insights into Phases of Liquid Water from Study of Its Unusual Glass-Forming Properties , 2008, Science.

[56]  I. R. Mcdonald,et al.  Simple Liquid Metals , 1990 .

[57]  A. Einstein.  Die Plancksche Theorie der Strahlung und die Theorie der spezifischen Wärme [AdP 22, 180 (1907)] , 2005, Annalen der Physik.

[58]  E. Holleran.  An equation of state for gases and liquids , 1982 .

[59]  V. Prakapenka,et al.  The COMPRES/GSECARS gas-loading system for diamond anvil cells at the Advanced Photon Source , 2008 .

[60]  G. Ruocco,et al.  Dynamics of Dense Supercritical Neon at the Transition from Hydrodynamical to Single-Particle Regimes , 1998 .

[61]  H. S. Green,et al.  A Kinetic Theory of Liquids , 1947, Nature.

[62]  Keiji Watanabe,et al.  Critical-like behaviour of glass-forming liquids. , 2010, Nature materials.

[63]  J. Hansen,et al.  Basic Concepts for Simple and Complex Liquids , 2003 .