The enlargement kinetics of the block structure of a growing crystal

The mechanism behind the enlargement of the block structure of a growing crystal (resulting from the system's tendency to decrease the block boundary energy) is suggested and analyzed. The size distribution of the blocks and the law governing structural enlargement on the planar crystallization front upon either isothermal growth of the crystal or temperature gradient growth are found. Numerical estimates are made, and it is shown that for small blocks (less than 0.01-0.001 cm) the enlargement distribution over time takes on a linear character, whereas for large blocks this distribution obeys a logarithmic law. It is also shown that, on the macroscopically convex crystallization front, structural enlargement occurs more rapidly (exponentially) than on the planar front.