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

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