Dislocation multiplication in materials with high lattice friction

In many materials there is a strong, thermally activated, interaction between moving dislocations and the crystal lattice. In such cases, dislocations parallel to dense crystallographic rows exhibit a low mobility.

In silicon (left), the lattice resistance originates from the covalent bonding. The densest rows are lying along the three 110 directions of the 111 slip planes.

In BCC Fe (right), the lattice resistance is due to a slight three-dimensional entension of the screw dislocation cores. Screw dislocations have a low mobility, whereas non-screw dislocations are highly mobile. Hence, dislocation loops are significantly extended along the 111 screw directions. The motion of screw dislocations governs plastic flow. In these two examples, use is made of periodic boundary conditions.

film_Si.mp4
film_source_BCC.mp4