Preferential alignment is produced for the NL8 thermal double donors (TDDs) when uniaxial stress is applied during their formation at∼450 °C. The recovery kinetics reveal that they can reorient readily on the time scale of their lifetime and their individual alignments therefore reflect the strain fields that each introduces into the lattice. Analysis reveals that each of the donor cores produces large compressional strain along its C2v[001]′axis, the magnitude of which decreases monotonically with increase in the TDD species series, suggesting strain relief as the mechanism for nearby oxygen accumulation. The rate and activation energy for the reorientation suggests that the process is limited by the diffusion motion of the nearby interstitial oxygen atoms, with∼5 jumps being required for TDD3, the third in the series, and progressively more for the subsequent ones. ©1997 American Institute of Physics.