Mixing and phase separation in molecular fluid mixtures

Ali, I.; Osman, S. M.; Sulaiman, Nidhal; Singh, Ranjit

doi:10.1080/00268970310001608432

Cited by 3 publications

(4 citation statements)

References 22 publications

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“…An anomalous property of the α-exp-6 potential, however, is that at a small distance r c in the region of high temperature (T > 2000 K), the potential reaches a maximum value and in the limit r → 0, it diverges to −∞ [18]. As suggested in [4,19] the double Yukawa potential u DY may be considered as advantageous since it can fit many other forms of empirical potentials, and, in addition, the related integral equation of the Helmholtz free energy and compressibility factor can be solved analytically:…”

Section: Double Yukawa For the He-h 2 Systemmentioning

confidence: 92%

“…In such a situation the contribution to the free energy is predicted to be arising from both enthalpic and entropic effects. According to [4] the smaller value of α (compared to 1) should drive the mixtures towards demixing.…”

Section: Double Yukawa For the He-h 2 Systemmentioning

confidence: 99%

“…In the case of a He-H 2 mixture a complication arises from the slight non-sphericity of H 2 . In order to overcome this difficulty, following Ali et al [4], we make use of the shape factor for the treatment of the model as a hard convex body derived from the hard spheres system. The application of such a tool, which is based on the scaling theory as proposed by Largo and Solana [5], is an advanced method for dealing with the nonsphericity of the constituents.…”

Section: Introductionmentioning

confidence: 99%

“…Ali et al and others have used the Wigner-Kirkwood expansion (see [4]) to take into account to first order quantum effects of such a system. But after having checked and compared with experimental thermodynamical properties, we found that the Wigner-Kirkwood expansion diverges at temperatures below 50 K even if we extend the quantum correction to second order.…”

Section: Introductionmentioning

confidence: 99%

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Equation of state and stability of the helium-hydrogen mixture at cryogenic temperature

Safa

Pfenniger

2008

Eur. Phys. J. B

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The equation of state and the stability of the helium-molecular hydrogen mixture at cryogenic temperature up to moderate pressure are studied by means of current molecular physics methods and statistical mechanics perturbation theory. The phase separation, segregation and hetero-coordination are investigated by calculating the Gibbs energy depending on the mixture composition, pressure and temperature. Low temperature quantum effects are incorporated via cumulant approximations of the Wigner-Kirkwood expansion. The interaction between He and H2 is determined by Double Yukawa potentials. The equation of state is derived from the hard sphere system by using the scaled particle theory. The behavior of the mixture over a wide range of pressure is explored with the excess Gibbs energy of mixing and the concentration fluctuations in the long wavelength limit. The theory is compared to cryogenic data and Monte-Carlo calculation predictions. Contrary to previous similar works, the present theory retrieves the main features of the mixture below 50 K, such as the critical point and the condensation-freezing curve, and is found to be usable well below 50 K. However, the method does not distinguish the liquid from the solid phase. The binary mixture is found to be unstable against species separation at low temperature and low pressure corresponding to very cold interstellar medium conditions, essentially because H2 alone condenses at very low pressure and temperature, contrary to helium. PACS. 64.10.+h General theory of equations of state and phase equilibria -64.75.Gh Phase separation and segregation in model systems (hard spheres, Lennard-Jones, etc.) -64.75.Ef Mixing

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Section: Double Yukawa For the He-h 2 Systemmentioning

confidence: 92%

Section: Double Yukawa For the He-h 2 Systemmentioning

confidence: 99%