Crossover between liquid-like and gas-like behaviour in CH4 at 400 K
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.
Keywords
Cite
@article{arxiv.1710.04212,
title = {Crossover between liquid-like and gas-like behaviour in CH4 at 400 K},
author = {D. Smith and M. A. Hakeem and P. Parisiades and H. E. Maynard-Casely and D. Foster and D. Eden and D. J. Bull and A. R. L. Marshall and A. M. Adawi and R. Howie and A. Sapelkin and V. V. Brazhkin and J. E. Proctor},
journal= {arXiv preprint arXiv:1710.04212},
year = {2017}
}
Comments
Uploaded version with higher resolution figures on 23/10/17. Accepted in Physical Review E