  The thermodynamics of phase transitions of binary solutions into spatially
inhomogeneous one-dimensional states is studied theoretically with taking into
account nonlinear effects. It is shown that below the spinodal decomposition
temperature there first occurs a phase stratification, and at a lower
temperature, after reaching the maximum possible stratification, there occurs a
second-order transition into the phase with concentration waves. The
contribution of inhomogeneity to the entropy and heat capacity of phases is
calculated and the phase diagram in the coordinates temperature and average
concentration is constructed.

Statistical Mechanics