A terahertz study of taurine: Dispersion correction and mode couplings

• Published in: The Journal of chemical physics 2017-03, Vol.146 (12), p.124119-124119
• Main Authors: Dai, Zelin, Xu, Xiangdong, Gu, Yu, Li, Xinrong, Wang, Fu, Lian, Yuxiang, Fan, Kai, Cheng, Xiaomeng, Chen, Zhegeng, Sun, Minghui, Jiang, Yadong, Yang, Chun, Xu, Jimmy
• Format: Article
• Language: English
• Subjects: Computer simulation; Couplings; Density functional theory; Dispersion; Empirical analysis; Oscillators; Spectrum analysis
• ISSN: 0021-9606; 1089-7690
• DOI: 10.1063/1.4978896

The low-frequency characteristics of polycrystalline taurine were studied experimentally by terahertz (THz) absorption spectroscopy and theoretically by ab initio density-functional simulations. Full optimizations with semi-empirical dispersion correction were performed in spectral computations and vibrational mode assignments. For comparison, partial optimizations with pure density functional theory were conducted in parallel. Results indicate that adding long-range dispersion correction to the standard DFT better reproduces the measured THz spectra than the popular partial optimizations. The main origins of the observed absorption features were also identified. Moreover, a coupled-oscillators model was proposed to explain the experimental observation of the unusual spectral blue-shift with the increase of temperature. Such coupled-oscillators model not only provides insights into the temperature dynamics of non-bonded interactions but also offers an opportunity to better understand the physical mechanisms behind the unusual THz spectral behaviors in taurine. Particularly, the simulation approach and novel coupled-oscillators model presented in this work are applicable to analyze the THz spectra of other molecular systems.