can best be described as a ring breathing mode of both pyridyl rings, with contribution from the attached phenyl rings and minor contributions from the acac ligand; in mode 125, the two pyridyl rings are out of phase, while in mode 126 they are in phase. In contrast, the dominant vibration mode in Ir(ppy)2(pic) is best described as a ring breathing mode of the aryl rings in a single ppy ligand.