Abstract
The gamma-aminobutyric acid (GABA) is the most important inhibitory
neurotransmitter in vertebrate central nervous systems. Taking full
account of the measured X-ray diffractogram of its stable monoclinic
polymorph, we have performed density functional theory (DFT)
calculations to analyze/understand its infrared and Raman spectra
considering its monoclinic polymorph, an isolated stabilized (120)
plane, and a single GABA molecule. Besides, phonon dispersion/density of
states, heat capacity, Debye temperature, and entropy/enthalpy/free
energies were also obtained for the GABA monoclinic crystal. Vibrational
signatures due to the GABA (120) planes are pointed out for the first
time for several wavenumbers. The results obtained for the GABA
monoclinic polymorph reinforce the need of dispersion-corrected
solid-state calculations to describe the vibrational properties of
molecular crystals instead of considering a single isolated molecule
picture, even for wavenumbers larger than those usually associated with
lattice modes.
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