Table 2: Scaled force constants for the citric acid dimer.

Description Dimera Monomerb B3LYP/6-31G* HF/4-21G f (ν O–H) 6.61 6.84 f (ν C–C) 3.92 4.34 f (ν C=O) 12.06 13.38 f (ν CH2) 4.89 5.35 f (ν C–O) 6.07 6.11 f ( CH2) 0.75 0.55 f (wag CH2) 1.15 0.65

Units in mdyn Å−1 for stretching and mdyn Å rad−2 for angle deformations. aThis work. bFrom [15].