Infrared and Raman spectroscopy and DFT calculations of DL amino acids: Valine and lysine hydrochloride

Abstract Single crystals of DL-valine and DL-lysine hydrochloride were grown by slow evaporation method and the crystallographic structure were confirmed by X-ray diffraction experiment and Rietveld method. These two crystals have been studied by Raman spectroscopy in the 25–3600 cm −1 spectral range and by infrared spectroscopy through the interval 375–4000 cm −1  at room temperature. Experimental and theoretical vibrational spectra were compared and a complete analysis of the modes was done in terms of the Potential Energy Distribution (PED).