Spontaneous onion-structure formation from planar lamellar nuclei.

Nucleation and growth are a basic elementary process of ordering. The nucleation process is controlled by a competition between interfacial and bulk energy. Thus an ordered structure of a nucleus at its birth is not necessarily the most stable thermodynamically: Ostwald step rule. In addition to this, we found the topological transformation of nuclei from the most stable bulk structure (planar lamella) to a metastable one (onion) in a lyotropic liquid crystal. This indicates that the fate of nuclei of low-dimensional internal order can also be seriously affected by an additional competition between interfacial and elastic deformation energy.