SPINODAL INSTABILITY OF SUSPENSIONS OF LARGE SPHERES IN A FLUID OF SMALL SPHERES

Numerical solutions of the thermodynamically self-consistent RY integral equation for the pair structure of a binary fluid hard sphere mixture, of size ratio sigma-1/sigma-2 = 0.1, exhibit divergent concentration fluctuations when the partial packing fractions of the two species are comparable, i.e. at low concentration of large spheres. This spinodal instability is studied at constant pressure, and it is shown that phase separation sets in for a reduced pressure P* = P-sigma-1(3)/k(B)T in the range 10(-2) < P* < 10(-1).