Elastic energies of dissociated Frank loops in f.c.c. metals and alloys

Elastic energies of dissociated non-regular hexagonal Frank loops have been calculated in the approximation of isotropic linear elasticity theory. A model has been used in which attractive Shockley dislocations could eventually recombine. It has been shown that small loops are strongly dissociated provided that the stacking fault energy is not too high. This is a possible explanation for black spot defects. An evolution scheme for loop growth is suggested. In particular, Frank loops and stacking fault tetrahedra could have a similar origin to that considered in early studies of vacancy clustering.