Department of Chemistry, Syracuse University, 1-014 Center for Science & Technology, Syracuse, New York 13244-4100, USA.
J Phys Chem A. 2011 Oct 13;115(40):11039-44. doi: 10.1021/jp204750v. Epub 2011 Sep 16.
The terahertz (THz) spectra of crystalline solids are typically uniquely sensitive to the molecular packing configurations, allowing for the detection of polymorphs and hydrates by THz spectroscopic techniques. It is possible, however, that coincident absorptions may be observed between related crystal forms, in which case careful assessment of the lattice vibrations of each system must be performed. Presented here is a THz spectroscopic investigation of citric acid in its anhydrous and monohydrate phases. Remarkably similar features were observed in the THz spectra of both systems, requiring the accurate calculation of the low-frequency vibrational modes by solid-state density functional theory to determine the origins of these spectral features. The results of the simulations demonstrate the necessity of reliable and rigorous methods for THz vibrational modes to ensure the proper evaluation of the THz spectra of molecular solids.
太赫兹（THz）光谱通常对晶体固体的分子堆积构型具有独特的敏感性，允许通过太赫兹光谱技术检测多晶型物和水合物。然而，在相关晶体形式之间可能观察到巧合吸收，在这种情况下，必须对每个系统的晶格振动进行仔细评估。本文介绍了柠檬酸在无水和一水合物相中的太赫兹光谱研究。在两个系统的太赫兹光谱中都观察到了非常相似的特征，这需要通过固态密度泛函理论准确计算低频振动模式来确定这些光谱特征的起源。模拟结果表明，为了确保对分子固体的太赫兹光谱进行正确评估，需要可靠和严格的太赫兹振动模式方法。
