Takahashi Masae, Okamura Nubuyuki, Fan Xinyi, Shirakawa Hitoshi, Minamide Hiroaki
Graduate School of Agricultural Science, Tohoku University , Sendai 980-0845, Japan.
RIKEN Advanced Science Institute , Sendai 980-0845, Japan.
J Phys Chem A. 2017 Apr 6;121(13):2558-2564. doi: 10.1021/acs.jpca.6b11049. Epub 2017 Mar 28.
We have investigated the terahertz-spectral property of nicotinamide focusing on the temperature dependence in the range of 14-300 K. We observed that almost all peaks in the terahertz spectrum of the nicotinamide crystal showed a remarkable shift with temperature, whereas the lowest-frequency peak at 34.8 cm showed a negligible shift with temperature. By analyzing the terahertz spectrum with the dispersion-corrected density functional theory calculations, we found that the difference in the temperature dependence of the peak shift is well understood in terms of the presence/absence of stretching vibration of the intermolecular hydrogen bond in the mode and the change of cell parameters. The anharmonicity in the dissociation potential energy of very weak intermolecular hydrogen bonding causes the remarkable peak shift with temperature in the terahertz spectrum of nicotinamide. This finding suggests that the assignment and identification of peaks in the terahertz spectrum are systematically enabled by temperature-dependent measurements.
我们研究了烟酰胺在14 - 300 K范围内的太赫兹光谱特性，并着重关注了其温度依赖性。我们观察到，烟酰胺晶体太赫兹光谱中的几乎所有峰都随温度发生了显著位移，而34.8 cm处的最低频率峰随温度的位移可忽略不计。通过用色散校正密度泛函理论计算分析太赫兹光谱，我们发现，根据模式中分子间氢键拉伸振动的有无以及晶胞参数的变化，可以很好地理解峰位移温度依赖性的差异。非常弱的分子间氢键解离势能中的非谐性导致了烟酰胺太赫兹光谱中峰随温度的显著位移。这一发现表明，通过依赖温度的测量可以系统地实现太赫兹光谱中峰的归属和识别。
