THz spectral analysis of barbituric acid and its dihydrate

The THz absorption spectrum of barbituric acid has been investigated utilizing terahertz time-domain spectroscopy (THz-TDS). The vibrational spectra of barbituric acid and its dihydrate have been studied in the framework of density functional theory using Perdew-Burke-Ernzerhof functional. In addition, the comparison of THz patters between barbituric acid and its anhydrate were also performed. It is found that four distinct THz spectral peaks and two shoulder peaks are exhibited in barbituric acid measurement. Peak assignment implies that all measured features come from the intermolecular forces. For barbituric acid dihydrate, three absorption peaks are predicted, which comes from the interactions of barbituric acid and barbituric acid molecules, barbituric acid and water molecules in solid-state. Finally, these different spectral patters indicate the ability of THz spectra to identify hydrate from anhydrate in practice.