X-ray diffraction study and models of liquid methane at 92 K

Abstract

New x-ray diffraction data for liquid methane near the triple point are presented. The data are analyzed using molecular scattering factors for methane which permit extraction of the carbon–carbon structure and correlation functions. Several site–site pair potentials are used with the reference interaction site model (RISM) to predict the structure and correlation functions for a dense methane-like fluid, and these are compared to the structure and correlation functions derived from the diffraction study. In addition, the accuracy of RISM is assessed by comparison with published computer simulation calculations on methane. Our results indicate that although the RISM distribution functions for ’’tetrahedral’’ molecules such as methane hae some physically unrealistic features, they compare well with molecular dynamics results. Site–site interaction potentials give an adequate description of liquid methane, provided that attractive forces are included in the potential. Although methane molecules are ’’seen’’ by x rays as spherically symmetric, orientational correlations between pairs of neighboring molecules are clearly present in the liquid near the triple point.

Thermodynamic, Structural and Transport Properties of Lennard-Jones Liquid Systems. A Molecular Dynamics Simulations of Liquid Helium, Neon, Methane and Nitrogen

“…At a temperature of T=92K°, the g(r) from X-ray diffraction gives a number of nearest neighbours ≈12 molecules and the number of neighbours in the second layer of about ≈ 55 [6]. Sesé [3] has obtained similar radial distribution function to those of the present calculations ( Fig.…”

“…The literature shows that these systems are widely investigated in both experimental and theoretical ways [1][2][3][4][5]. X-rays scattering of liquid methane near the triple point (90.7 K°) [6][7][8][9][10], and liquid nitrogen [11] were studied. Theoretically new simulations with path-integral formalism have been conducted to obtain thermodynamic properties, and the quantum radial functions involving Feynmann-Hibbs potentials were used for liquid helium [12].…”

A Refined Intermolecular Interaction Potential for Methane: Spectral Analysis and Molecular Dynamics Simulations

“…One is a phase point far from the triple point but close to the melting line 50 while the other is a supercritical point. [51][52] A schematic plot of these phase points is shown in Figure 3.…”

Adaptive resolution molecular-dynamics simulation: Changing the degrees of freedom on the fly

“…The number of nearest neighbors in the first layer corresponding to the first minimum in the RDF cm is about 11. For comparison, the corresponding experimental value from X-ray diffraction for liquid methane at T = 92 K is approximately 12 [47].…”