ELSEVIER 5 January 1996 Chemical Physics Letters 248 (1996) 57-62 CHEMICAL PHYSICS LETTERS Solution of the associative Percus-Yevick approximation for the multicomponent mixture of dimerizing hard spheres with surface adhesion I.A. Protsykevich, Yu. Duda, M.F. Holovko Ukrainian National Academy of Sciences, Institute for Condensed Matter Physics, 1 Svientsitsky Street, 290011 Lviv, Ukraine Received 28 July 1995 Abstract An analytical solution of the two-density Ornstein-Zernike equation closed by the associative Percus-Yevick approxima- tion for the multicomponent mixture of dimerizing adhesive hard spheres (DAHS) is obtained in closed form. This is the generalization of the previous solution for the one-component DAHS model, which has been proposed for the description of protein effect on the properties of reverse micelles. Although the solution is illustrated by its application to the structure of the two-component model, it can be easily utilized for the arbitrary number of components. Recently much effort has been focused toward the theoretical study of the association effects in liquids. In particular, a number of simple models have been proposed and investigated using Wertheim's theory of associating fluids [1] and an approximation which is based on Baxter's sticky potential [2]. Among them there is a dimerizing adhesive hard sphere (DAHS) model, which accounts for van der Waals interaction as well as interaction creating chemical bonds. This model can be used for the description of the protein effect on the properties of reverse mi- celles [3,4]. The structure, thermodynamic and perco- lation of the DAHS model has been discussed in Refs. [3-9]. In this Letter, we are extending our previous analysis [5,6,10] to the more general case of multi- component DAHS. We are presenting here an analyt- ical solution of the orientationally averaged version of the associative Percus-Yevick (APY) approxima- tion [1,11] for the M-component mixture of DAHS with different sizes and numbers of particles, and different surface adhesive and associative interparti- cle interactions. The pairwise interaction between particles of type a and b for the present model is described by Uab(r) : Ua(hS)(r) + Ua~baax)(r) + U~SS)(Z), (1) where U~b~S)(r) is the hard-sphere potential, Ua(~aX)(r) is Baxter's sticky potential [2], and U~(~s~)(z) is the associative potential which appears due to the off- center attractive site. Here z is the distance between the sites of two particles at a given center-center separation and orientation. The value of z is set so that conditions of steric incompatibility are satisfied [1], i.e. due to the steric reasons each site can bond only one partner. To provide analytic treatment of the present model we will consider it within the sticky-point limiting 0009-2614/96/$12.00 © 1996 Elsevier Science B.V. All fights reserved SSDIOOO9-2614(95)O1277-X