The paper considers the method for determining stable low angle cell boundaries. The multilevel physical approach is applied to model inelastic deformation, using which shears are found for slip systems of the crystal. Based on these data, the density of two types of dislocation defects, which are stopped during deformation at crystallite boundaries, is introduced into consideration. The optimization problem is posed for finding sections of the boundary with reduced energy. The dependence of orientation of these sections relative to the crystallographic coordinate system is investigated. The results of solving the optimization problem and their analysis are presented.