ABSTRACT
In what follows it will be shown that KH2PO4-family crystals grow by the dislocation mechanism. A screw dislocation emerging onto a face forms a non-vanishing step. Crystallizing matter attaching to the step twists it into a spiral. As a result a dislocation hillock appears and spreads out across the face and at the normal to it thereby causing the crystal to grow. Our aim is to discuss the peculiarities of this mechanism.
