Abstract
To explain the orientational relations in c-axes between each component for the polycrystalline snow crystals, such as twin prisms, spatial and radiating dendrites, and combination of bullets, a cubic structure model accompanied by CSL boundaries is proposed at the stage of formation of polycrystalline nucleus. The formation mechanism of stacking fault and cubic structure nucleus is studied by means of two-dimensional nucleation model. It is shown that the condition under which the crystals are divided into twin prisms and polycrystalline crystals (spatial type and radiating type, etc.) depends on the degrees of supercooling and the dimensions of cubic structure.
