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Properties of ferrofluid bilayer (modeled as a system of two planar layers separated by a h and each layer carrying a soft sphere dipolar liquid) are calculated in the framework of inhomogeneous Ornstein-Zernike equations with reference hypernetted chain closure (RHNC). The bridge functions are taken from a soft sphere (1/r12) reference system in the pressure-consistent closure approximation. In order to make the RHNC problem tractable, the angular dependence of the correlation functions is expanded into special orthogonal polynomials according to Lado. The resulting equations are solved using the Newton-GRMES algorithm as implemented in the publicdomain solver NITSOL. Orientational densities and pair distribution functions of dipoles are compared with Monte Carlo simulation results. A numerical algorithm for the Fourier-Hankel transform of any positive integer order on a uniform grid is presented. [ABSTRACT FROM AUTHOR]

A new Monte Carlo simulation method designed for polymer solutions confined to planar slits is presented. The slit is in equilibrium with a surrounding bulk solution and the method allows a variation of the slit width while maintaining the polymer chemical potential constant. This is achieved by changing the tangential pressure as a function of slit width. An analysis of chain parameters and monomer distribution within the slit has been carried out. The model system used is supposed to mimick a macromolecular solution whose stability is manipulated by addition of adsorbing and/or nonadsorbing polymers. Generally, for the nonadsorbing polymer an attractive depletion force is found. At high volume fractions the attraction is reduced and a repulsive force appears at short separations. The depletion force can also be extinguished in the case of an adsorption potential of intermediate strength, while strong adsorption gives rise to a significant attraction due to polymer bridges. © 2000 American Institute of Physics. [ABSTRACT FROM AUTHOR]

A polymer density functional theory (P-DFT) has been extended to the case of quantum statistics within the framework of Feynman path integrals. We start with the exact P-DFT formalism for an ideal open chain and adapt its efficient numerical solution to the case of a ring. We show that, similarly, the path integral problem can, in principle, be solved exactly by making use of the two-particle pair correlation function (2p-PCF) for the ends of an open polymer, half of the original. This way the exact data for one-dimensional quantum harmonic oscillator are reproduced in a wide range of temperatures. The exact solution is not, though, reachable in three dimensions (3D) because of a vast amount of storage required for 2p-PCF. In order to treat closed paths in 3D, we introduce a so-called "open ring" approximation which proves to be rather accurate in the limit of long chains. We also employ a simple self-consistent iteration so as to correctly account for the interparticle interactions. The algorithm is speeded up by taking convolutions with the aid of fast Fourier transforms. We apply this approximate path integral DFT (PI-DFT) method to systems within spherical symmetry: 3D harmonic oscillator, atoms of hydrogen and helium, and ions of He and Li. Our results compare rather well to the known data, while the computational effort (some seconds or minutes) is about 100 times less than that with Monte Carlo simulations. Moreover, the well-known "sign problem" is expected to be considerably reduced within the reported PI-DFT, since it allows for a direct estimate of the corresponding partition functions.