抄録
In complex crystals which contain groups of atoms bonded strongly with each other such as anionic radicals, complex ions and hydrated cations, low-frequency rotational vibrations of these groups of atoms may be expected to exist in addition to low-frequency translational vibrations, as in the case of ideal molecular crystals. By using an one-dimensional lattice, the modes of these vibrations are analysed. According to the results obtained, we may conclude that new additional modes appear, which is related to the rotational vibrations of the groups of atoms, and they may be classified, in general, into the optical and acoustical branches just as in the case of the translational vibrations. In addition, the effects of the introduction of these new modes upon the specific heat at low temperatures are investigated, by using the results of the analysis for the one-dimensional lattice.
