Argon

Argon (Ar) has long been a popular choice for computer simulations of simple liquids. Some of the first computer simulations of liquid argon were those of Wood and Parker in 1957 and of Rahman in 1964 . Sadus and Prausnitz have shown that three-body repulsion makes a significant contribution to three-body interactions in the liquid phase (for use of the Axilrod-Teller interaction see ). However, the generic Lennard-Jones model has been frequently used due to its simplicity; some parameters are quoted in the next section. A specific interatomic potential for Ar has been proposed by Aziz .

Thermophysical properties (experimental)

Property	Temperature	Pressure
Triple point	83.8058 K	69 kPa
Critical point	150.87 K	4.898 MPa
Melting point	83.80 K
Boiling point	87.30 K

Models

Lennard-Jones parameters

The Lennard-Jones model for argon (Rowley, Nicholson and Parsonage parameters).

A selection of parameters for the Lennard-Jones model for liquid argon are listed in the following table:

Authors	$\epsilon /k_{B}$ (K)	$\sigma$ (nm)	Reference (year)
Rahman	120	0.34	(1964)
Barker, Fisher and Watts	142.095	0.33605	(1971)
Rowley, Nicholson and Parsonage	119.8	0.3405	(1975)
White	125.7	0.3345	parameter set #4 (1999)

Buckingham potential

The Buckingham potential for argon is given by (Eq. 27 ):

$E(r)=1.69\times 10^{-8}e^{-r/0.273}-102\times 10^{-12}r^{-6}$

where $E$ is in ergs ( 10⁻⁷ J) and $r$ in Å.

BBMS potential

The Bobetic-Barker-Maitland-Smith potential .

Radial distribution function

Radial distribution function

Nucleation

Nucleation

Virial equation of state

Virial equation of state

Viscosity

Viscosity .

Heat capacity

Heat capacity .

Surface tension

Surface tension .

Liquid-vapour coexistence

.

References

Related material

• H. C. Longuet-Higgins and B. Widom "A rigid sphere model for the melting of argon", Molecular Physics 8 pp. 549-556 (1964)
• D. Henderson and J. A. Barker "On the solidification of argon", Molecular Physics 14 pp. 587-589 (1968)
• F. Lado "Numerical Calculation of the Density Autocorrelation Function for Liquid Argon", Physical Review A 5 pp. 2238-2244 (1972)
• Ali Asghar Davoodi and Farzaneh Feyzi "A new approach for long range corrections in molecular dynamics simulation with application to calculation of argon properties", Journal of Molecular Liquids 150 pp. 33-38 (2009)
• Jonas Wiebke, Elke Pahl, and Peter Schwerdtfeger "Sensitivity of the thermal and acoustic virial coefficients of argon to the argon interaction potential", Journal of Chemical Physics 137 064702 (2012)
• C. Fan, D.D. Do, D. Nicholson and E. Ustinov "Chemical potential, Helmholtz free energy and entropy of argon with kinetic Monte Carlo simulation", Molecular Physics 112 pp. 60-73 (2014)
• Nikolay P. Malomuzh, and Konstantin S. Shakun "Specific properties of argon-like liquids near their spinodals", Journal of Molecular Liquids 235 155-162 (2017)
• Gábor Rutkai, Monika Thol, Roland Span and Jadran Vrabec "How well does the Lennard-Jones potential represent the thermodynamic properties of noble gases?", Molecular Physics 115 pp. 1104-1121 (2017)
• Maryna Vlasiuk and Richard J. Sadus "Ab initio interatomic potentials and the thermodynamic properties of fluids", Journal of Chemical Physics 147 024505 (2017)