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Updated: Jul 6, 2025

HKUST-1 as a Heterogeneous Catalyst for the Synthesis of Vanillin
Published on: July 23, 2016
Harmonic and anharmonic studies on THz spectra of two vanillin polymorphs
Yin Li1, Li Xu2, Jinbo Ouyang2
1School of Physics and Materials Science, Nanchang University, Xuefu Avenue 999, Nanchang City 330031, China.
Abstract:
Polymorphism commonly exists in organic molecular crystals. The fingerprint features in low-frequency vibrational range are important information reflecting different intermolecular interactions of polymorphs. Interpreting these features is very helpful to understand vibrational property of polymorphs and reveal the thermodynamic stability. In this work, the low-frequency vibrations of form I and II of vanillin are investigated using terahertz time-domain spectroscopy. Static DFT calculation and ab initio molecular dynamics (AIMD) are employed to interpret their low-frequency vibrations of both forms in harmonic and anharmonic ways, respectively. Their low-frequency vibration characteristics in harmonic calculations are discussed, and anharmonic mode couplings between OH bond stretch and the stretching and bending motion of hydrogen bonds are uncovered. Moreover, the thermodynamic energies including electronic potential energy and vibrational/kinetic energy arising from nuclear motions are calculated. The result reveals that the stability order of the two forms is mainly dependent on their electric potential energy difference.
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