Abstract：This study focuses on benzoic acid and sorbic acid, using a terahertz time-domain spectroscopy (Terahertz Time-Domain Spectroscopy, THz-TDS) system to measure the experimental spectra of their pure substances and mixed pellets in the 0.5~2.2 THz range.After preprocessing the spectral data, the two substances' terahertz (Terahertz, THz) absorption spectra were obtained. The qualitative identification of the above two substances can be accurately achieved based on the peak positions of the characteristic absorption peaks in the absorption spectra. In this paper, the dimer cluster configurations of the benzoic acid and sorbic acid mixture were constructed using the Genmer component. Structural optimizations, frequency calculations, and screening were conducted for their single molecules, unit cells, and mixture clusters using density functional theory (DFT). The potential energy distribution was used to analyze the vibration modes of the characteristic absorption peaks. Combining the simulated spectra with two interaction visualization methods—Independent Gradient Model based on Hirshfeld atom partitioning (IGMH) and the Interaction Region Indicator (IRI)—the vibration modes of abnormal absorption peaks in the mixed pellet were identified. The molecular and intermolecular interaction features were also visualized. The study found that the special absorption peaks in the simulated spectra of the mixture cluster configuration were caused by hydrogen bond vibrations between molecules. This further illustrates that the characteristic absorption peaks of benzoic acid, sorbic acid, and their mixtures in the terahertz frequency range mainly originate from collective vibration modes induced by intermolecular hydrogen bonds and intramolecular chemical bonds. By constructing and screening cluster configurations of mixed systems, this work deeply investigates the causes of characteristic absorption peaks in the terahertz absorption spectra of mixtures. It highlights the impact of intramolecular and intermolecular interactions and hydrogen bond effects on absorption peaks. This study introduces a novel method for characterizing crystal structures, significantly enhancing the accuracy and reliability of spectral interpretation for mixed systems. It also lays a foundation for subsequent quantitative analyses based on spectral data.
李文文，燕 芳，刘洋硕. 苯甲酸和山梨酸混合物的太赫兹吸收峰形成机理解析[J]. 光谱学与光谱分析, 2025, 45(07): 1848-1856.
LI Wen-wen, YAN Fang, LIU Yang-shuo. A Mechanistic Analysis of Terahertz Absorption Peak Formation in
Benzoic Acid and Sorbic Acid Mixtures. SPECTROSCOPY AND SPECTRAL ANALYSIS, 2025, 45(07): 1848-1856.
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