Thermophysical Properties of the Lennard-Jones Fluid: Database and Data Assessment

Abstract

Literature data on thermophysical properties of the Lennard-Jones fluid, which were sampled with Molecular Dynamics and Monte Carlo simulations, were reviewed and assessed. The literature data was complemented by simulation data from the present work that was taken in regions in which previously only sparse data was available. Data on homogeneous state points (for given temperature T and density ρ: pressure p, thermal expansion coefficient α, isothermal compressibility β, thermal pressure coefficient γ, internal energy u, isochoric heat capacity c v , isobaric heat capacity c p , Grüneisen coefficient Γ, Joule-Thomson coefficient µ JT , speed of sound w, Helmholtz energy a, chemical potential µ, surface tension γ) was considered as well as data on the vapor-liquid equilibrium (for given T : vapor pressure p s , saturated liquid and vapor densities ρ and ρ , enthalpy of vaporization ∆h v). The entire set of available data, which contains about 35,000 data points, was digitalized and included in a database, which is made available in the electronic supplementary material of this paper. Different consistency tests were applied to assess the accuracy and precision of the data. The data on homogeneous states were evaluated point-wise using data from their respective 1 vicinity and equations of state. Approximately 5% of all homogeneous bulk data were discarded as outliers. The vapor-liquid equilibrium data were assessed by tests based on the compressibility factor, the Clausius-Clapeyron equation, and by an outlier test. Seven particularly reliable vapor-liquid equilibrium data sets were identified. The mutual agreement of these data sets is approximately ±1% for the vapor pressure, ±0.2% for the saturated liquid density, ±1% for the saturated vapor density, and ±0.75% for the enthalpy of vaporizationexcluding the region close to the critical point.

Characteristic Curves of the Lennard-Jones Fluid

“…The second and third virial coefficient computed from the 20 considered LJ EOS are compared in Fig. 1 with exact data obtained from statistical mechanics [ 81 ] published in the literature [ 7 , 29 , 60 , 82 – 84 ]. Numbers from our implementation perfectly agree with that literature data.…”

“…The numeric values of these computer experiment data were summarized in Ref. [7] and are taken here as reference.…”

“…The Lennard-Jones (12,6) potential [1,2] has been extensively used since the early days of computer simulation [3][4][5][6] for the modeling of repulsive and dispersive interactions of simple fluids. It is probably the most frequently investigated monomer model fluid in molecular simulation [7]. The Lennard-Jones (LJ) potential can be favorably used for testing new theories and simulation methods, e.g., for mixtures, phase changes, non-equilibrium phenomena, and interfaces between phases [8][9][10][11][12][13][14][15][16][17][18][19].…”

“…As Brown's characteristic curves are directly related to virial coefficients, also the second and third virial coefficient are studied. This comparison is of particular interest, since the virial coefficients of the LJ fluid can be computed exactly from their definitions in statistical mechanics, while reference data obtained from computer simulations are subject to errors and uncertainties [7,71,72]. Brown's characteristic curves and the virial coefficients are directly linked in the limit of the ideal gas and therefore corporately investigated in the present work.…”

Simulation‐based equations of state for the Lennard‐Jones fluid: Apparent success and hidden failure

“…Therefore, the study of other thermodynamic properties at certain state conditions might reveal different results. Conclusive and comprehensive comparisons among the MPS‐LJ EOSs are feasible since reliable and comprehensive data of thermophysical properties of LJ fluid are now available in the literature 54‐56 . Because this subject is broad, we leave it for future studies.…”