Ruggiero Michael T, Zeitler J Axel, Erba Alessandro
Department of Chemical Engineering and Biotechnology, University of Cambridge, Philippa Fawcett Drive, Cambridge, CB3 0AS, UK.
Dipartimento di Chimica, Universitá di Torino, via Giuria 5, Torino, Italy.
Chem Commun (Camb). 2017 Mar 28;53(26):3781-3784. doi: 10.1039/c7cc00509a.
The intermolecular anharmonic potential of crystalline purine is probed by means of temperature-dependent terahertz time-domain spectroscopy, low-frequency Raman scattering, X-ray diffraction, and ab initio quasi-harmonic quantum-chemical simulations. As temperature increases, anharmonicity in the intermolecular interactions results in strongly anisotropic thermal expansion - with a negative thermal expansion along the b crystallographic axis - yielding corresponding bulk structural modifications. The observed thermally-induced shifts of most vibrational bands in the terahertz region of the spectra are shown to arise from volume-dependent thermal changes of the hydrogen-bond pattern along the a and b crystallographic axes.
通过温度相关的太赫兹时域光谱、低频拉曼散射、X射线衍射以及从头算准谐量子化学模拟，对结晶嘌呤的分子间非谐势进行了探究。随着温度升高，分子间相互作用中的非谐性导致强烈的各向异性热膨胀——沿b晶轴方向出现负热膨胀——从而产生相应的整体结构变化。光谱太赫兹区域中大多数振动带的热致位移表明，这是由氢键模式沿a和b晶轴的体积相关热变化引起的。
