Structure and Dynamics of Orientational Defects in Ice

Orientational defects play an important role in a variety of ice phenomena, such as dielectric and mechanical relaxation, and electrical conductivity. In this study, structure and migration mechanisms of such defects were investigated using molecular dynamics simulations. Defect structure is quite different from the one proposed originally by Bjerrum [Science 115, 385 (1952)]. Two basic structures were identified for the $D$ defect (with excess OH in the network), and one dominant structure was obtained for the $L$ defect (with a missing hydrogen bond). Typically, one water molecule in a defect is displaced $\approx 1Å$ from the crystal lattice site. Defect jumps occur via vibrational phase coincidence.