Department of Chemistry, Syracuse University, Syracuse, New York 13244, USA.
J Phys Chem A. 2010 Dec 2;114(47):12513-21. doi: 10.1021/jp107597q. Epub 2010 Nov 4.
The high-resolution waveguide terahertz (THz) time-domain spectra (20-100 cm(-1)) of the two structural isomers 1,2-dicyanobenzene (1,2-DCB) and 1,3-dicyanobenzene (1,3-DCB) have been modeled and assigned using solid-state density functional theory. The THz spectra of these similar molecules are distinctly different in the low-frequency region with the differences being driven by modifications of the crystal packing arrangement between the isomers. Simulations utilizing the hybrid density functionals B3LYP and PBE0 were performed to determine the origins of the observed vibrational features. External lattice vibrations (hindered translations and rotations) are found to dominate these spectra, reinforcing the need for proper solid-state models in the analysis of the THz spectra of organic molecular solids. These calculations were able to account for all of the observed spectral features exhibited by both isomers, even in the case of 1,2-DCB, where the spectrum was found to be the result of two coexisting crystalline polymorphs.
利用固态密度泛函理论，对两种结构异构体 1,2-二氰基苯（1,2-DCB）和 1,3-二氰基苯（1,3-DCB）的高分辨率波导太赫兹（THz）时域光谱（20-100 cm(-1)）进行了建模和归属。这些相似分子的太赫兹光谱在低频区域明显不同，差异是由异构体之间晶体堆积排列的修饰引起的。利用混合密度泛函 B3LYP 和 PBE0 进行了模拟，以确定观察到的振动特征的起源。发现外部晶格振动（受阻平移和旋转）主导了这些光谱，这强调了在分析有机分子固体的太赫兹光谱时需要适当的固态模型。这些计算能够解释两种异构体所表现出的所有观察到的光谱特征，即使对于 1,2-DCB 也是如此，其中发现光谱是两种共存的晶型的结果。
