The role of attractive forces in the structure of simple liquids: a theory for small-angle scattering
- 10 July 1981
- journal article
- Published by IOP Publishing in Journal of Physics C: Solid State Physics
- Vol. 14 (19), 2569-2579
- https://doi.org/10.1088/0022-3719/14/19/008
Abstract
Examines the role of attractive forces in determining the static structure factor S(q) for simple liquids. By treating these forces in a random-phase approximation and the repulsive forces in a blip function expansion about a hard-sphere reference system the authors derive explicit results for the coefficients of q2, q3 and q4 in the expansion of c(q), the Fourier transform of the Ornstein-Zernike direct correlation function of a Lennard-Jones liquid, they show that the attractive forces ensure that alpha , the coefficient of q2, is negative for most thermodynamic states. This implies that even near the triple point a simple (argon-like) liquid should exhibit 'residual' Ornstein-Zernike behaviour, i.e. there should be a shallow minimum in S(q) for q approximately=0.25AA-1. The authors find that the short-range correlation length, R=(- alpha rho )1/2 varies weakly with density rho and with temperature. Their calculated value for R at the critical point is in good agreement with results obtained from radiation scattering experiments on Ar and Kr near their critical points. The q3 term is associated with r-6 asymptotic behaviour of the interatomic potential. The authors analysis suggests that it may be possible to detect such a contribution, if it is present in a real liquid, by X-ray or neutron diffraction.Keywords
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