Theoretical and spectroscopic studies of vibrational spectra of hydrogen bonds in molecular crystal of β-oxalic acid

Infrared spectra of β-oxalic acid and its deuterated derivative have been measured. Experimental geometry and frequencies are compared with the results of DFT and ab initio calculations performed at the B3LYP/6-31++G**, B3LYP/cc-pVTZ, B3PW91/6-31++G**, B3PW91/cc-pVTZ and MP2/6-31++G** levels. The calculated geometries and frequencies agree well with the experimental data.