Liquid argon radial distribution function

Fig. 6.2 Radial distribution function determined from a lOOps molecular dynamics simulation of liquid argon at a temperature of 100K and a density of 1.396gcm. ...

Figure 9.24 A radial distribution function (RDF) for a DRP of monospheres (right) and a scheme for its evaluation (left), Nmeenl4nR2 is an equivalent of IA(R), where A/mean is the mean number of spheres in the intervals of 0.2R. The solid curve illustrates the data obtained from neutron diffraction in liquid argon 1,2 are the experimental data by Scott [128] and Bernal [127] obtained for the models of steel spheres (cited in [127]).

Figure 6 The radial distribution function for a Lennard-Jones model of liquid argon at a temperature T = 300 K. A simulation cell of 35 A containing 864 atoms with periodic boundary conditions was used. The simulation was carried out by coupling each degree of freedom to an MTK thermostat, and the equation of motion was integrated using the methods discussed in Ref. 28.

Zwanzig, Kirkwood, Oppenheim, and Alder38 have numerically evaluated Eq. 47 for liquid argon at its normal boiling point, using the same Bom-Green radial distribution function g0<2) and the same numerical values for the frictional coefficient and for the constants in the intermolecular potential function shear viscosity coefficient for the same substance. The value obtained was x — 4.1 x 10-4 cal/g—sec—°K which is in reasonable agreement with the experimental value of 2.9 x 10-4. 

In the case of pure liquids numerical computations for the transport coefficients in argon, krypton, and xenon have been carried out by Palyvos et al. using a modified Lennard-Jones potential and the radial distribution function of Kirkwood, Lewinson, and Alder. The results, for instance for argon, represent percentages betw een 60 and 90% of the experimental values in a wide range of temperatures and densities. Besides, they agree with experiment better than the results derived from the Kirkwood of Rice-AIInatt types of theories. 

Figure A2.4.1. Radial distribution function g(R ) for water (dashed curve) at 4 °C and 1 atm and for liquid argon (full curve) at 84.25 K and 0.71 atm as functions of the reduced distance R =R/o, where a is the molecular diameter from [1].

The radial distribution function of a liquid is intermediate between the solid and the gas, with a small number of peaks as short distances, superimposed on a steady decay to a constant value at longer distances. The radial distribution function calculated from a molecular dynamics simulation of liquid argon (shown in Figure 6.2) is typical. For short distances (less... 

Figure 5 A typical radial distribution function for liquid argon.

Figure 6.3 Radial distribution function, g(r), where r is interatomic separation, for liquid argon at 85 K.

Figm e 6.T shows the radial distribution function, g r), for liquid argon. To understand the details of this plot of g(r), examine the environment around a given Ar atom in the liquid, as illustrated in Figure 6.4. 

Fig. 6.33. The radial distribution function g R) for liquid argon computed by Rahman (1964) by the method of molecular dynamics. The Lennard-Jones parameters = 0.81 and ejkT = 1.35. [Redrawn with changes from Rahman and Stillinger (1971).]...

Liquid water also has tetrahedral symmetry because the melting process is not disruptive enough to disorder the water molecules fully. This is known from the radial distribution functions for liquid water that are observed in x-ray and neutron-diffraction experiments. Figure 29.6 shows the radial distribution functions of two liquids, water, and argon. 

The work involved in the same process carried out in liquid argon can be obtained from the experimental radial distribution function. From Fig. 7.6 we estimate (assuming that g R) has the same form at room temperature)... 

A liquid has a certain amount of short-range order around each molecule, when each molecule is taken as the origin for the radial distribution function of the molecules around it. This claim has been verified for liquid argon and CFaCl on the basis of x-ray diffraction studies. In other words, although a liquid does not have the kind of long-range order found... 

Much can be explained by reference to the radial distribution function of liquid water (Fig. 2). The broken line is the radial distribution function of liquid water and the drawn out line is the radial distribution function of liquid argon. Both are normalized to the respective molecular diameters so that at R = 1 we find the nearest neighbor molecule, and so on. 

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