On the growth mechanism of polycrystalline snow crystals with a specific grain boundary

Observed frequently in a natural snowfall at temperatures lower than -20°C, the crossed-plate crystal is an assemblage of two to four thin basal plates, each plate extending along a CSL grain boundary with a relation of 70.3°/[11$\text{2}$0]. A possible growth mechanism is proposed to account for the characteristics growth in the direction of the axis [11$\text{2}$0]. If two or more grain boundary dislocation (GBD) structures are contained at a CSL grain boundary, growth layers will overflow alternately on the (10$\text{1}$0) planes of each component crystal at the intersection of these planes. Thus, the distinctive structure of the CSL grain boundary, like the feature of a screw dislocation step, will induce the preferential growth in this direction.