Orientational defects in hexagonal ice were investigated using molecular dynamics simulations. Energy relaxation during L- and D-defect migration was shown to be associated with improved alignment of water molecules along the local electric fields. Two new forms of defects, an "L+D complex," and a "5+7 defect," were characterized. These forms appear in ice trajectories close to the melting point, and in the course of L- and D-pair recombination process. Defect pair recombination was shown to be a complex process, involving collective H-bond changes in groups of molecules. (C) 2004 American Institute of Physics.