Transport properties of the Lennard-Jones truncated and shifted fluid from non-equilibrium molecular dynamics simulations

Abstract

The thermal conductivity λ, shear viscosity η, and self-diffusion coefficient D of the Lennard-Jones fluid truncated and shifted at the cut-off radius r c = 2.5 σ (LJTS fluid) are determined for a wide range of thermodynamic states (T * = [0.6, 10.0] and ρThe simulations are carried out using a non-equilibrium molecular dynamics (NEMD) method that was introduced recently and in which two gradients are applied simultaneously. It is shown that the two-gradient method is well-suited for studies of liquid and supercritical states. Data for λ, η, and D for about 350 state points are reported. Two variants of the simulation method, which differ in the accuracy and efficiency, are explored and found to yield consistent data. Correlations for λ, η, and Dρ of the LJTS fluid are provided. The data and the correlations are compared to literature data of Lennard-Jones (LJ) type fluids and good agreement is observed. The truncation of the LJ potential causes a slight increase in D, while it has no significant effect on λ and η.

Modified Entropy Scaling of the Transport Properties of the Lennard-Jones Fluid

“…Lautenschlaeger 42 3.2% 3.9% λ* Bugel 67 4.1% 6.8% ρ*D* Lautenschlaeger 42 11.3% 951.5% ρ*D* Ruckenstein 127 12.4% 12.3% ρ*D* Rowley 59 667.7% 153.0%…”

“…The critical enhancement complicates the application of excess-entropy scaling because isomorph theory is not expected to be valid in the vicinity of the critical point, 124 and therefore, knowledge of the excess entropy Figure 16. Deviation plot for the secondary self-diffusion data sets 42,42,[46][47][48][50][51][52][53]58,70,71 compared with the correlation from eq 58. The range of the ordinate from −20% to 20% is linearly scaled, and logarithmically scaled outside this range.…”

“…Model Comparison. There are several empirical models available in the literature for the transport properties of the Lennard-Jones fluid; Lautenschlaeger and Hasse 42 provided a small review of the existing models. These empirical models were generally fit to the simulations carried out by the author who proposed the model.…”

Reaction-field electrostatics in molecular dynamics simulations: development of a conservative scheme compatible with an atomic cutoff

“…96,108,[111][112][113][114][115] The SW and SH approaches have also been applied to electrostatic interactions in complement to mean-field schemes, for example in the switched RF approach, 116 or in variants of the Wolf-damping method. 114,[117][118][119][120][121][122] In view of the small LJ forces at typical cutoff distances, the application of SH or SW schemes to the LJ interactions has been less frequently considered, 109,111,123 although it may still be useful if one wishes to enforce a strict energy conservation in simulations. Note that SH and SW schemes are irrelevant in the lattice-sum case, where the cutoff is only a numerical parameter and the level of noise is (nearly) exclusively controlled by the accuracy of the reciprocal-space evaluation.…”

Thermal and caloric properties of fluids from non-equilibrium molecular dynamics simulations using the two-gradient method

“…The main characteristics of the two-gradient method were already discussed in detail in [1,2]. They are only briefly summarized here: The pressure in the simulation box is constant even for large temperature gradients and velocity gradients.…”