Strain Fields And Crystallographic Characteristics Of Interstitial Dislocation Loops of Various Geometry In BCC Iron

The formation energy, the relaxation volume, the dipole-force tensor, the self strain tensor and strain fields of interstitial dislocation loops in bcc iron (clusters of self interstitial atoms) have been calculated by molecular statics. Hexagonal and square dislocation loops of different types with different Burgers vectors, directions of dislocation segments and habit planes containing up to ~2500 self-interstitials have been considered. Analytical expressions describing size dependence of the formation energy, the relaxation volume and the self strain tensor for the loops stated have been obtained. The most energetically favorable loops are hexagonal loops with Burgers vector a/2'' and habit plane {11x}, where x takes values in the range from 0 to 1 depending on the loop size. The formation energy of a'' loops with '' and '' dislocation segments is ~14% and 23% greater than that of hexagonal a/2'' loops at N > 500, respectively. The analysis of the formation energies of a/2'' and a'' loops demonstrated that the nucleation of an a'' loop by joining of two a/2'' loops is possible when the total number of constituent self-interstitials in these loops is larger than 13.