The thermal conductivity of argon in the critical region

Transport coefficients of the Lennard-Jones model fluid. III. Bulk viscosity

In an extensive computer simulation study, the transport coefficients of the Lennard-Jones model fluid were determined with high accuracy from equilibrium molecular-dynamics simulations. In the frame of time-correlation function theory, the generalized Einstein relations were employed to evaluate the transport coefficients. This third of a series of four papers presents the results for the bulk viscosity. With comprehensive simulation data at over 350 state points, the temperature and density dependences of the bulk viscosity are characterized in this work over a wide range of fluid states. The bulk viscosity exhibits a large critical enhancement similar to that known for the thermal conductivity, but it extends much farther into the supercritical region and can be observed even at 4.5 times the critical temperature. An investigation of the pressure-fluctuation autocorrelation functions shows that the enhancement is caused by extremely slowly decaying pressure fluctuations.

Determination of potential energy functions of argon, krypton, and xenon via the inversion of reduced-viscosity collision integrals at zero pressure

The pair potential energy functions of argon, krypton, and xenon have been determined via the inversion of reduced-viscosity collision integrals at zero pressure. A comparison of the potentials with the previously determined potentials are included. The viscosity and thermal conductivity of argon, krypton, and xenon at different temperatures and pressures have been calculated and compared with experimental values. The present potentials for argon, krypton, and xenon provide a good overall account of the experimental properties of these compounds, considering the stated uncertainty in the measurements.Key words: potential energy function, collision integral, viscosity, thermal conductivity.

Crossover parametric equation of state for Ising-like systems

We present a parametric equation for the thermodynamic properties in the critical region of three-dimensional Ising-like systems which include fluids and fluid mixtures. The equation of state incorporates a crossover from singular Ising behavior asymptotically close to the critical point to classical (mean-field) behavior further away from the critical point, characterized by two physical crossover parameters: a coupling constant related to the strength and range of molecular interactions and a "cutoff" wave number for the critical fluctuations. In the asymptotic Ising limit, the crossover equation reproduces the most recent theoretical estimates for the universal ratios of the leading and correction-to-scaling critical amplitudes. The equation has been tested by comparing it with recent experimental thermodynamic-property data for 3He near its vapor-liquid critical point.