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Collective dynamics in liquid Si under high pressure above the melting line minimum. J Mol Liq 2022. [DOI: 10.1016/j.molliq.2022.121116] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
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Bryk T, Gorelli FA, Mryglod I, Ruocco G, Santoro M, Scopigno T. Behavior of Supercritical Fluids across the "Frenkel Line". J Phys Chem Lett 2017; 8:4995-5001. [PMID: 28945381 DOI: 10.1021/acs.jpclett.7b02176] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
The "Frenkel line" (FL), the thermodynamic locus where the time for a particle to move by its size equals the shortest transverse oscillation period, has been proposed as a boundary between recently discovered liquid-like and gas-like regions in supercritical fluids. We report a simulation study of isothermal supercritical neon in a range of densities intersecting the FL. Specifically, structural properties and single-particle and collective dynamics are scrutinized to unveil the onset of any anomalous behavior at the FL. We find that (i) the pair distribution function smoothly evolves across the FL displaying medium-range order, (ii) low-frequency transverse excitations are observed below the "Frenkel frequency", and (iii) the high-frequency shear modulus does not vanish even for low-density fluids, indicating that positive sound dispersion characterizing the liquid-like region of the supercritical state is unrelated to transverse dynamics. These facts critically undermine the definition of the FL and its significance for any relevant partition of the supercritical phase.
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Affiliation(s)
- T Bryk
- Institute for Condensed Matter Physics of the National Academy of Sciences of Ukraine , 1 Svientsitskii Street, UA-79011 Lviv, Ukraine
- Institute of Applied Mathematics and Fundamental Sciences, Lviv Polytechnic National University , UA-79013 Lviv, Ukraine
| | - F A Gorelli
- Istituto Nazionale di Ottica INO-CNR , I-50019 Sesto Fiorentino, Italy
- European Laboratory for Non Linear Spectroscopy, LENS , I-50019 Sesto Fiorentino, Italy
| | - I Mryglod
- Institute for Condensed Matter Physics of the National Academy of Sciences of Ukraine , 1 Svientsitskii Street, UA-79011 Lviv, Ukraine
| | - G Ruocco
- Dipartimento di Fisica, Universita di Roma La Sapienza , I-00185 Roma, Italy
- Center for Life Nano Science @Sapienza, Istituto Italiano di Tecnologia , 295 Viale Regina Elena, I-00161 Roma, Italy
| | - M Santoro
- Istituto Nazionale di Ottica INO-CNR , I-50019 Sesto Fiorentino, Italy
- European Laboratory for Non Linear Spectroscopy, LENS , I-50019 Sesto Fiorentino, Italy
| | - T Scopigno
- Dipartimento di Fisica, Universita di Roma La Sapienza , I-00185 Roma, Italy
- Center for Life Nano Science @Sapienza, Istituto Italiano di Tecnologia , 295 Viale Regina Elena, I-00161 Roma, Italy
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Bryk T, Huerta A, Hordiichuk V, Trokhymchuk AD. Non-hydrodynamic transverse collective excitations in hard-sphere fluids. J Chem Phys 2017; 147:064509. [PMID: 28810767 DOI: 10.1063/1.4997640] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Collective excitations in hard-sphere fluids were studied in a wide range of wave numbers and packing fractions η by means of molecular dynamics simulations. We report the observation of non-hydrodynamic transverse excitations for packing fractions η≥0.395 in the shape of transverse current spectral functions. Dispersion of longitudinal excitations in the whole range of packing fractions shows a negative deviation from the linear hydrodynamic law with increasing wave numbers even for dense hard-sphere fluids where the transverse excitations were observed. These results do not support a recent proposal within the "Frenkel line" approach that the positive sound dispersion in liquids is defined by transverse excitations. We report calculations of the cutoff "Frenkel frequencies" for transverse excitations in hard-sphere fluids and discuss their consistency with the estimated dispersions of shear waves.
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Affiliation(s)
- Taras Bryk
- Institute for Condensed Matter Physics of the National Academy of Sciences of Ukraine, 1 Svientsitskii Street, UA-79011 Lviv, Ukraine
| | - Adrian Huerta
- Facultad de Física, Universidad Veracruzana, Circuito Gonzalo Aguirre Beltrán s/n Zona Universitaria Xalapa, Veracruz C.P. 91000, Mexico
| | - V Hordiichuk
- Institute for Condensed Matter Physics of the National Academy of Sciences of Ukraine, 1 Svientsitskii Street, UA-79011 Lviv, Ukraine
| | - A D Trokhymchuk
- Institute for Condensed Matter Physics of the National Academy of Sciences of Ukraine, 1 Svientsitskii Street, UA-79011 Lviv, Ukraine
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