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Behavior of Supercritical Fluids across the "Frenkel Line"
T Bryk1,2, F A Gorelli3,4, I Mryglod1
1Institute for Condensed Matter Physics of the National Academy of Sciences of Ukraine , 1 Svientsitskii Street, UA-79011 Lviv, Ukraine.
The Journal of Physical Chemistry Letters
|September 26, 2017
Summary
The Frenkel line (FL) in supercritical fluids is challenged by new simulations. Findings suggest the FL does not mark distinct liquid-like and gas-like regions, questioning its significance.
Area of Science:
- Thermodynamics
- Fluid Dynamics
- Computational Physics
Background:
- The Frenkel line (FL) is a proposed boundary distinguishing liquid-like and gas-like states in supercritical fluids.
- It is defined by the ratio of particle dynamics to oscillation periods.
Purpose of the Study:
- To investigate the validity of the Frenkel line as a phase boundary.
- To analyze structural and dynamic properties of supercritical neon around the FL.
Main Methods:
- Molecular dynamics simulations of supercritical neon.
- Analysis of pair distribution functions and dynamic properties (transverse excitations, shear modulus).
Main Results:
- Pair distribution functions show smooth evolution across the FL, indicating medium-range order.
- Low-frequency transverse excitations exist below the Frenkel frequency.
- High-frequency shear modulus remains non-zero in low-density fluids.
Conclusions:
- The Frenkel line's definition and significance for partitioning supercritical fluids are critically undermined.
- Observed dynamics do not support the FL as a boundary for distinct supercritical fluid regions.
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