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Manuscript Title: HNCR: a program to calculate the structure and thermodynamics of binary mixtures of charged hard spheres.
Authors: E. Lomba, J.S. Hoye
Program title: HNCR
Catalogue identifier: ACGL_v1_0
Distribution format: gz
Journal reference: Comput. Phys. Commun. 69(1992)420
Programming language: Fortran.
Computer: VAX 9210.
Operating system: VMS, VM/CMS, AIX, UNIX BSD.
RAM: 200K words
Word size: 32
Keywords: Statistical physics, Thermodynamics, Ionic fluids, Binary mixtures, Hypernetted chain Equation, Integral equations.
Classification: 23.

Nature of problem:
The problem is the calculation of the correlation functions in a binary mixture of charged hard spheres with arbitrary sizes and charges (primitive model of electrolytes). From these, the thermodynamic properties of the system (internal energy, thermodynamics potentials, pressure and isothermal compressibility) are evaluated.

Solution method:
The pair correlation functions are obtained by solving the Orstein- Zernike integral equation with the Hypernetted Chain approximation closure (HNC). This is done expressing the mixture equation in matrix form. The solution is obtained by applying a hybrid of the Newton-Raphson method with a mixing iterates procedure. Thermodynamic properties are obtained by integration of the correlation functions g alpha beta(r) and c alpha beta(r). The use of the Kinoshita-Harada iteration strategy makes the program particularly useful for calculations involving several state points (density and temperature) for a given system.

Restrictions:
Only hard core potentials are supported. At present, the program is restricted to binary mixtures (one component electrolytes or molten salts).

Running time:
The test job using 2048 integration points and performing Newton-Raphson iterations on 35 of these points takes 47 seconds on a VAX 9210; with 256 integration points and 15 points involved in the Newton-Raphson algorithm, the running time is 3.12 seconds. This figures rise to 15 minutes and 64 seconds in an desktop IBM PS/2 70-A21 running AIX.