A new algorithm for the simulation of a Frank-Read source in materials with directional bonding was used to check a recently proposed model for deformation twinning in diamond-cubic semiconductors. In this algorithm, a segment of a perfect dislocation that was pinned at its ends (source dislocation) was assumed to lie along a (110) Peierls valley. This developed into a semi-hexagonal loop under the application of a resolved shear stress. It was noted that previous simulations had not taken account of a temperature dependence of the operation of the Frank-Read source. However, it was recalled here that, in covalent materials with directional bonding, thermal activation played a predominant role in dislocation motion. Therefore, the temperature was taken into account here via the thermal activation of kink pairs and its influence upon the dislocation velocity. Simulations of a 60° source dislocation suggested that the critical stress was very temperature-sensitive. It was shown that, in most cases, the back-stress was much smaller than the line tension. As a result, the continuous operation of previously emitted loops that were based upon a nascent dislocation brought the operation of the Frank-Read source to a temporary halt. Thus, the number of loops which halted the operation of the Frank-Read source was highly stress- and temperature-sensitive.

T.Geipel, F.Banhart: Computational Materials Science, 1996, 7[1-2], 181-6