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We demonstrate that the pair potential V(r) in one-dimensional systems can be obtained analytically from the pair-distribution function in case of short-ranged interactions. We re-examine the exact statistical mechanics solution and propose a simple procedure for extracting the pair potential and the equation of state from experimentally measured pair-distribution functions. The method is applied to charge-stabilised colloids which are confined to a one-dimensional laser trap. published

We introduce long-range weight functions to the framework of fundamental measure theory (FMT) of the non-uniform, single-component hard-sphere fluid. While the range of the usual weight functions is equal to the hard-sphere radius R, the modified weight functions have range 3R. Based on the augmented FMT, we calculate the radial distribution function g(r) up to second order in the density within Percus' test particle theory. Consistency of the compressibility and virial routes on this level allows us to determine the free parameter γ of the theory. As a side result, we obtain a value for the fourth virial coefficient B 4 which deviates by only 0.01% from the exact result. The augmented FMT is tested for the dense fluid by comparing results for g(r) calculated via the test particle route to existing results from molecular dynamics simulations. The agreement at large distances (r > 6R) is significantly improved when the FMT with long-range weight functions is used. In order to improve agreement close to contact (r = 2R) we construct a free energy which is based on the accurate Carnahan-Starling equation of state, rather than the Percus-Yevick compressibility equation underlying standard FMT.

Morphological thermodynamics is employed to calculate the depletion potential between two big hard spheres in a solvent of small spheres. Thereby, the potential is characterized solely by the geometric properties of the solvent-accessible surface of the two-sphere configuration in the depletion region. Comparison with explicit density functional theory calculations using accurate functionals of the fundamental measure type shows good agreement.