UMR CNRS-Université Bordeaux 1 n° 5255, Institut des Sciences Moléculaires , 351, Cours de la Libération, 33405 Talence, France.
J Phys Chem B. 2012 May 17;116(19):5719-28. doi: 10.1021/jp300103b. Epub 2012 May 4.
Molecular dynamics simulations of liquid quinoline have been performed at experimental densities corresponding to the temperature range 276-320 K. The intermolecular potential is a simple effective two-body potential between rigid molecules having 17 atomic Lennard-Jones and electrostatic Coulomb interaction sites. The vaporization enthalpy is overestimated by 8-9% with respect to the experimental value. The translational diffusion coefficient exhibits a small non-Arrhenius behavior with a change in temperatures near 290 and 303 K. The rotational diffusion tensor is rotated around the z axis perpendicular to the molecular plane by an angle of 4-6° with respect to the frame of reference defined by the principal axes of inertia. The rotational diffusion tensor presents a significant anisotropy with D(rot,y)/D(rot,x) ≃ 0.6-0.5 and D(rot,z)/D(rot,x) ≃ 1.6-1.3 between 276 and 320 K when the x axis is defined as the long molecular axis and the y axis is situated nearly along the central C-C bond. The rotational diffusion coefficients, the reorientational correlation times of the C-H vectors, and the T1(13)C NMR relaxation times present a non-Arrhenius break around 288-290 K in agreement with several experimental results. In addition, a non-Arrhenius break can also be observed at 303 K for these properties. It has been found that the structure evolves smoothly in the studied temperature range. Center of mass-center of mass and atom-atom radial distribution functions show a monotonous evolution with temperature. Various types of first-neighbor dimers have been defined, and their population analysis has revealed a continuous monotonous evolution with temperature. Thus, the non-Arrhenius behavior observed for translational and rotational diffusion is correlated with the monotonous evolution of the population of first-neighbor dimers at a microscopic level and not with a sharp structural transition.
已在实验密度下对液态喹啉进行了分子动力学模拟，实验密度对应于 276-320 K 的温度范围。分子间势是刚性分子之间的简单有效两体势，具有 17 个原子 Lennard-Jones 和静电库仑相互作用位点。与实验值相比，汽化焓高估了 8-9%。平移扩散系数表现出小的非 Arrhenius 行为，在 290 和 303 K 附近的温度变化。旋转扩散张量围绕垂直于分子平面的 z 轴旋转，相对于由惯性主轴定义的参考系旋转 4-6°。在 276 和 320 K 之间，当 x 轴定义为长分子轴且 y 轴沿中央 C-C 键时，旋转扩散张量呈现出显著的各向异性，D(rot,y)/D(rot,x)≃0.6-0.5，D(rot,z)/D(rot,x)≃1.6-1.3。旋转扩散系数、C-H 矢量的重新取向相关时间和 T1(13)C NMR 弛豫时间在 288-290 K 左右呈非 Arrhenius 断裂，与几个实验结果一致。此外，这些性质在 303 K 也可以观察到非 Arrhenius 断裂。发现结构在研究的温度范围内平滑演变。质心-质心和原子-原子径向分布函数随温度单调变化。已定义了各种类型的第一邻域二聚体，其种群分析揭示了随温度的连续单调变化。因此，平移和旋转扩散的非 Arrhenius 行为与微观层面上第一邻域二聚体种群的单调演化有关，而不是与急剧的结构转变有关。
