Journal of Molecular Structure vol:298 pages:155-163
A theoretical model is presented that accounts for the pressure dependence of the low-frequency modes of liquid amides. The recently discovered low-frequency Raman bands originate from the hindered rotational (librational) motion of the molecules. The present theory explains the higher librational frequency found for amides with hydrogen bonds compared to the one found in amides which do not form hydrogen bonds. The pressure dependences of the two types of amide are also systematically different. These differences can be quantitatively predicted by the present theory.