Crystalline 2-pyridone has been investigated using terahertz vibrational spectroscopy in the range of 10 90 cm (1) (0.3-2.7 THz). Solid-state density functional theory (B3LYP, BP, and PW91 with the 6-311G(d, p) basis set) was used to simulate and assign both observed terahertz spectral features and a previously published far-infrared spectrum up to 400 cm (1). The PW91 functional was found to provide the best combination of crystal structure and vibrational frequency reproduction. Observed spectral features below 150 cm (1) are assigned to intermolecular movements of the 2-pyridone chains within the unit cell. The use of independent intramolecular and intermolecular frequency scalars is proposed. (C) 2009 Elsevier B. V. All rights reserved.