Abstract. The mean spherical model is solved for two-component plasmas-fully ionised systems of two species of ions in a uniform neutralising background of electrons. The ion-ion potential is the sum of a bare Coulomb part and a hard-core part. The authors obtain the direct correlation functions C_ij(r) as polynomials in r and give the general solution (ions with different hard cores) up to a set of algebraic equations in the polynomial coefficients: these equations are then solved explicitly for the case of equal hard cores. For the particular case of a hydrogen-helium mixture the excess energy, the excess energy of mixing and the excess energy in a 'one-fluid model' for the two-component plasma are given for several values of coupling parameter and helium concentration: the comparison with Monte Carlo and hypernetted chain equation results is quite satisfactory in spite of the equal radii approximation. Some structure factors are also plotted for an H⁺-He²⁺ mixture.

Print publication: Issue 19 (10 July 1980)