Fluids in equilibrium with disordered porous materials. Integral equation theory

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Abstract
The Ornstein–Zernike equations previously introduced by two of the authors for a fluid in equilibrium within a quenched disordered matrix are solved numerically within the Percus–Yevick approximation. The structure of a fluid of hard spheres is reported for two types of microporous matrices: a sintered‐type structure of mutually penetrable (randomly placed) obstacles or sites, and a packed bed of quenched hard spheres. The integral‐equation results agree well with Monte Carlo simulation data also reported here. For the case of point obstacles, when both models coincide, the structure of the fluid is found to be insensitive to obstacle concentration. The structure of a hard‐sphere fluid in a bed of other quenched hard spheres is found to be significantly different from that of the equilibrium binary mixture of the two types of particles. Pressures and bulk‐pore partition coefficients are reported for beds of randomly placed obstacles. A sparse‐matrix approximation is presented and compared with the full solution. These are the first results for the equilibrium properties of fluids in disordered substrates.