Abstract
An expression for the intersection volume of four equi-sized spheres is derived. This expression is used to construct the four-point correlation function for a system of fully penetrable spheres dispersed in a matrix. The knowledge of this four-point correlation function enables us to numerically calculate the microstructural parameter B , that appears in the fourth-order bounds on the effective conductivity due to Phan-Thien & Milton ( Proc. R. Soc. Lond . A380, 333 (1982)).