RAMAN AND FAR-INFRARED SPECTRA OF FORMAMIDE AT TEMPERATURES DOWN TO 20-K

The Raman and infrared wavenumbers of solid HCONH2 and DCOND2 were mea sured at 20 K and high temperatures. More peaks were observed in both the lattice and internal mode regions than were expected from the know n structure, so the structure was redetermined. The resulting structur e is in agreement with earlier determinations, so the extra peaks are attributed to second-order effects produced by a large anharmonicity a ssociated with the hydrogen bonds. Attempts to model the structural de tails and the lattice dynamics had only a limited success, which may a gain be attributed to anharmonic effects and to the basic inadequacies of the models.