Numerical Solutions of the Convolution‐Hypernetted Chain Integral Equation for the Pair Correlation Function of a Fluid. II. The Hard‐Sphere Potential

1963 ◽  
Vol 39 (6) ◽  
pp. 1388-1397 ◽  
Author(s):  
Max Klein
Keyword(s):  
Integral Equation ◽  
Correlation Function ◽  
Pair Correlation Function ◽  
Hard Sphere ◽  
Numerical Solutions ◽  
Pair Correlation ◽  
Hypernetted Chain

scholarly journals The Kirkwood Superposition Approximation, Revisited and reexamined

2013 ◽  
Vol 1 (1) ◽  
pp. 27-35 ◽  
Author(s):  
Arieh Ben Naim
Keyword(s):  
Integral Equation ◽  
Correlation Function ◽  
Pair Correlation Function ◽  
Pair Correlation ◽  
Potential Of Mean Force ◽  
Superposition Approximation ◽  
Potential Of Mean Forces

The Kirkwood superposition approximation (KSA) was originally suggested to obtain a closure to an integral equation for the pair correlation function. It states that the potential of mean force of say, three particles may be approximated by sum of potential of mean forces of pairs of particles. Nowadays, this approximation is widely used, explicitly or implicitly, in many fields unrelated to the problem for which it was suggested.It is argued that the KSA is neither a good approximation nor a bad approximation; it is simply not an approximation at all.

Pair correlation function in a fluid with density inhomogeneities: results of the Percus‒Yevick and hypernetted chain approximations for hard spheres near a hard wall

1986 ◽  
Vol 404 (1827) ◽  
pp. 323-337 ◽  
Keyword(s):  
Correlation Function ◽  
Pair Correlation Function ◽  
Hard Spheres ◽  
Pair Correlation ◽  
Hard Wall ◽  
Bulk Fluid ◽  
Pair Correlations ◽  
Hypernetted Chain ◽  
Density Inhomogeneities ◽  
Bulk Case

Solutions for the pair correlation function and density profile of a system of hard spheres near a hard wall are obtained by using the Percus‒Yevick and hypernetted chain approximations, generalized for inhomogeneous fluids. The Percus‒Yevick (PY) results are similar in accuracy to those obtained for the bulk fluid. The PY pair correlation function is generally too small near contact but quite good overall. The hypernetted chain (h. n. c.) results are difficult to obtain numerically and are poorer than in the bulk. Often the h. n. c. pair correlations are too small at contact, in contrast to the bulk case where they are too large, although there are configurations where the contact values of the pair correlation function are too large. Nearly always the error in the h. n. c. results is much worse than is the case for the bulk. Both approximations are qualitatively satisfactory in that they predict the correct asymmetries between the values of the pair correlation functions for pairs of hard spheres whose line of centres is parallel or normal to the surface of the wall.

Decay of pair correlation functions

1977 ◽  
Vol 55 (9) ◽  
pp. 761-766 ◽  
Author(s):  
Yoshio Tago ◽  
William R. Smith
Keyword(s):  
Correlation Function ◽  
Correlation Length ◽  
Correlation Functions ◽  
Pair Correlation Function ◽  
Hard Sphere ◽  
Pair Correlation ◽  
Direct Correlation Function ◽  
Pair Correlation Functions ◽  
Hard Sphere Fluid

The decay equation, which determines the correlation length and the period of the pair correlation function of a fluid at large distances, is discussed using the Ornstein–Zernike equation when the direct correlation function vanishes rapidly at large distances. The decay equation is solved numerically using the exact hard sphere and sticky hard sphere fluid results from the Percus–Yevick approximation. In the case of the hard sphere fluid, oscillatory decay is always obtained. For the sticky hard sphere fluid, we obtain a locus both in the pressure–temperature plane and the density–temperature plane such that the decay is monotonic inside and oscillatory outside the locus.

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