On the Energy of the Hexagonal Frank Loop in Face Centred Cubic Metals

The energy of the hexagonal Frank loop is calculated taking into account the dissociation of the partial Frank dislocation surrounding the defect. This energy is compared to those obtained for such classical defects as circular or triangular Frank loops and a tetrahedron of stacking fault. The discussion is made in terms of stacking fault energy, shear modulus, and critical number of precipitated vacancies per defect.