Theoretical Investigation on the Terahertz Vibrational Spectroscopy of Amino acid Crystal

The terahertz (THz) theoretical spectra of solid-state amino acids were investigated in this paper. Based on the dispersion-corrected density functionals, the periodic crystal structures were constructed. It is found that B3LYP-D2 can produce more accurate simulation results, however, it also greatly increases the cost of calculations. The combination of PBE with the 6–311G(d.p) basis set is accurate enough to reproduce the experimental THz spectra of solid-state amino acids with much higher simulation speed. The observed spectral features were assigned as primarily external lattice translations and rotations with lesser contributions due to intramolecular torsions.