Crossover from gas-like to liquid-like molecular diffusion in a simple supercritical fluid
Year: 2024
Authors: Ranieri U., Formisano F., Gorelli F.A., Santoro M., Koza M.M., De Francesco A., Bove L.E.
Autors Affiliation: Univ Roma La Sapienza, Dipartimento Fis, Piazzale Aldo Moro 5, I-00187 Rome, Italy; Univ Edinburgh, Ctr Sci Extreme Condit, Edinburgh EH9 3FD, Midlothian, Scotland; Univ Edinburgh, Sch Phys & Astron, Edinburgh EH9 3FD, Midlothian, Scotland; CNR, IOM, INSIDE ILL, 71 Ave Martyrs, Grenoble 9, France; Inst Laue Langevin, 71 Ave Martyrs, Grenoble 9, France; Ctr High Pressure Sci & Technol Adv Res HPSTAR, 1690 Cailun Rd, Shanghai 201203, Peoples R China; Shanghai Adv Res Phys Sci SHARPS, Shanghai 201203, Peoples R China; CNR, INO, Via Nello Carrara 1, I-50019 Sesto Fiorentino, Fi, Italy; European Lab Nonlinear Spect, Via Nello Carrara 1, I-50019 Sesto Fiorentino, Fi, Italy; Ecole Polytech Fed Lausanne, Inst Phys, Lab Quantum Magnetism, CH-1015 Lausanne, Switzerland; Sorbonne Univ, UMR CNRS 7590, Inst Mineral Phys Mat & Cosmochim, 5 Pl Jussieu, F-75005 Paris, France.
Abstract: According to textbooks, no physical observable can be discerned allowing to distinguish a liquid from a gas beyond the critical point. Yet, several proposals have been put forward challenging this view and various transition boundaries between a gas-like and a liquid-like behaviour, including the so-called Widom and Frenkel lines, and percolation line, have been suggested to delineate the supercritical state space. Here we report observation of a crossover from gas-like (Gaussian) to liquid-like (Lorentzian) self-dynamic structure factor by incoherent quasi-elastic neutron scattering measurements on supercritical fluid methane as a function of pressure, along the 200 K isotherm. The molecular self-diffusion coefficient was derived from the best Gaussian (at low pressures) or Lorentzian (at high pressures) fits to the neutron spectra. The Gaussian-to-Lorentzian crossover is progressive and takes place at about the Widom line intercept (59 bar). At considerably higher pressures, a liquid-like jump diffusion mechanism properly describes the supercritical fluid on both sides of the Frenkel line. The present observation of a gas-like to liquid-like crossover in the self dynamics of a simple supercritical fluid confirms emerging views on the unexpectedly complex physics of the supercritical state, and could have planet-wide implications and possible industrial applications in green chemistry.
Journal/Review: NATURE COMMUNICATIONS
Volume: 15 (1) Pages from: 4142-1 to: 4142-10
More Information: We acknowledge the Institut Laue-Langevin for provision of beam time and Claude Payre, James Maurice, Eddy Lelievre-Berna, Jean Marc Zanotti and Quentin Berrod for advice and technical assistance during the experiment. We are grateful to Helmut Schober for having authorised the experiment at the ILL reactor. We acknowledge Luisa Scaccia for her invaluable contribution to making available the Bayesian analysis code written with A.D.F. We also acknowledge Ubaldo Bafile, Jose Teixeira and Francesco Sciortino for useful discussions. U.R. thanks the UKRI for financial support through the Future Leaders Fellowship MR/V025724/1 held by D. Laniel. L.E.B. acknowledges funding through the Swiss National Fund (FNS) grant n 212889 and the ANR-23-CE30-0034 EXOTIC-ICE. For the purpose of open access, the authors have applied a Creative Commons Attribution (CC BY) licence to any Author Accepted Manuscript version arising from this submission.KeyWords: Self-diffusion; Density-dependence; Dynamic Crossover; Widom Line; X-ray; Water; Methane; Coefficient; Equation; MotionsDOI: 10.1038/s41467-024-47961-7Citations: 1data from “WEB OF SCIENCE” (of Thomson Reuters) are update at: 2024-11-17References taken from IsiWeb of Knowledge: (subscribers only)