  We focus our attention on Monte Carlo simulations of crystallization, which
is one of the most important processes occurring in nature and technology of
materials. Special attention is paid to the crystallization shrinkage and its
consequences onto the growth of the new crystalline phase. We show that
crystallization shrinkage stops after reaching the percolation threshold and
that this is not the final stage of the crystallization process. Based on
experimental evidences on sintering of diopside-albite systems and computer
simulations we argue that crystallization continues inside the grains where the
remaining liquid melt is a subject of accumulation of stress and because the
stress relaxation by change in the volume is forbidden due to the already
formed rigid core, the so called crystallization induced porosity appears. We
show that even a relatively simple short range potential as the Lennard-Jones
one, reveals such a complicated phenomenon as the crystallization induced
porosity, which has a great importance onto the mechanical properties of the
newly crystallized material.
