STRUCTURE AND EVOLUTION OF NUCLEI OF A NE W PHASE DURING THE 1ST-ORDER PHASE-TRANSITION

On the basis of the generalized Ginzburg-Landau equation describing th e evolution of the order parameter field the nucleation process during the first-order phase transitions in two- and three-dimensional syste ms is studied. It is found that in the general case a critical nucleus is not spherical even in the system of isotropic symmetry and the siz e of typical nucleus is determined by the decay scale of the coupling responsible for the formation of disordered phase. The relaxation of a n arbitrary fluctuation field is analyzed. It is shown that spherical nuclei of sizes larger significantly than the wall thickness, supposed to be critical ones in the simple phenomenological theory, are essent ially supercritical and are formed only at the evolution stage late en ough.