Dynamic correlation of fluctuations during spinodal decomposition

The kinetics of the formation of order is studied for both a system with non-conserved one-component order parameter and a binary mixture with conserved order parameter (“spinodal decomposition”). By a decoupling of two-point probabilities a closed kinetic equation for the structure factor S(k, t1, t2) is obtained which describes the correlation of fluctuations at two times t1, t2 after the start of the nonlinear relaxation process. Both this dynamic structure factor and the cross section for inelastic scattering from such a decaying system far from equilibrium are calculated numerically for representative cases. The validity of the approximations made are discussed as well as the experimental observability of the departures found from equilibrium behavior.