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Crossover between liquid-like and gas-like behaviour in CH₄ at 400 K

Smith, D.; Hakeem, M. A.; Parisiades, P.; Maynard-Casely, H. E.; Foster, D.; Eden, D.; Bull, D. J.; Marshall, A. R.L.; Adawi, A. M.; Howie, R.; Sapelkin, A.; Brazhkin, V. V.; Proctor, J. E.

Authors

D. Smith

M. A. Hakeem

P. Parisiades

H. E. Maynard-Casely

D. Foster

D. Eden

D. J. Bull

A. R.L. Marshall

R. Howie

A. Sapelkin

V. V. Brazhkin

J. E. Proctor



Abstract

We report experimental evidence for a crossover between a liquid-like state and a gas-like state in fluid methane (CH₄). This crossover is observed in all of our experiments, up to 397 K temperature; 2.1 times the critical temperature of methane. The crossover has been characterized with both Raman spectroscopy and X-ray diffraction in a number of separate experiments, and confirmed to be reversible. We associate this crossover with the Frenkel line - a recently hypothesized crossover in dynamic properties of fluids extending to arbitrarily high pressure and temperature, dividing the phase diagram into separate regions where the fluid possesses liquid-like and gas-like properties. On the liquid-like side the Raman-active vibration increases in frequency linearly as pressure is increased, as expected due to the repulsive interaction between adjacent molecules. On the gas-like side this competes with the attractive Van der Waals potential leading the vibration frequency to decrease as pressure is increased.

Citation

Smith, D., Hakeem, M. A., Parisiades, P., Maynard-Casely, H. E., Foster, D., Eden, D., …Proctor, J. E. (2017). Crossover between liquid-like and gas-like behaviour in CH₄ at 400 K. Physical Review E, 96(5), https://doi.org/10.1103/PhysRevE.96.052113

Journal Article Type Article
Acceptance Date Oct 13, 2017
Online Publication Date Nov 9, 2017
Publication Date Nov 9, 2017
Deposit Date Oct 23, 2017
Publicly Available Date Nov 9, 2017
Journal Physical review. E, Statistical, nonlinear, and soft matter physics
Print ISSN 2470-0045
Electronic ISSN 2470-0053
Publisher American Physical Society
Peer Reviewed Peer Reviewed
Volume 96
Issue 5
Article Number 052113
DOI https://doi.org/10.1103/PhysRevE.96.052113
Public URL https://hull-repository.worktribe.com/output/455876
Publisher URL https://journals.aps.org/pre/abstract/10.1103/PhysRevE.96.052113
Copyright Statement ©2017 University of Hull
Additional Information This is a description of an article accepted for future publication in Physical review. E, Statistical, nonlinear, and soft matter physics

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