Theory for the Slowing Down of the Relaxation and Spinodal Decomposition of Binary Mixtures

The weak nonexponential relaxation t^-{a^'} recently found in computer experiments on the phase separation of alloys is explained in terms of a cluster reaction and diffusion process. The nonlinear features of this process can be accounted for by a time-dependent diffusion constant. Estimates for the resulting exponents a^'=1 (3+d) are consistent with the computer simulations. The experimental observability of this slowing down is discussed.