Structural stability of simple fluids and accuracy of integral-equation theories

The ability to describe the structural stability of a fluid may represent a stringent test for the overall physical soundness of an integral-equation theory. The accuracy of some approximate closures of the Ornstein-Zernike e quation is discussed in relation to the estimates of the density threshold of structural stability of the fluid that are obtained through an analysis of the iterative form of the integral equation. The connection with the ran dom-close-packing threshold of hard spheres is also investigated.