QM/MM and QM/QM/MM protocols are applied to the ab initio study of the three linear birefringences Kerr, Cotton–Mouton, and Jones, as shown by acetonitrile in the gas and pure liquid phases. The relevant first-order properties as well as linear, quadratic, and cubic frequency-dependent response functions were computed using time-dependent Kohn–Sham density-functional theory with use of the standard CAM-B3LYP functional. In the liquid phase, a series of room temperature (293.15 K) molecular dynamics snapshots were selected, for which averaged values of the observables were obtained at an optical wavelength of 632.8 nm. The birefringences were computed for electric and magnetic induction fields corresponding to the laboratory setup previously employed by T. Roth and G. L. J. A. Rikken in Phys. Rev. Lett., 2000, 85, 4478. Under these conditions, acetonitrile is shown to exhibit a weak Jones response—in fact roughly 6.5 times smaller than the limit of detection of the apparatus employed in the measurements mentioned above. A comparison is made with the corresponding gas-phase results and an assessment is made of the index of measurability, estimating the degree of overlap of the three birefringences in actual measurements. For acetonitrile, it is shown that this index is a factor of 3.6 and 6.7 larger than that of methylcyclopentadienyl-Mn-tricarbonyl and cyclohexadienyl-Fe-tricarbonyl, respectively—two compounds reported in Phys. Rev. Lett., 2000, 85, 4478 to exhibit a strong Jones signal.

中文翻译：

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液体乙腈中Kerr，Cotton-Mouton和Jones线性双折射的QM / MM和QM / QM / MM研究

QM / MM和QM / QM / MM协议适用于Kerr，Cotton-Mouton和Jones三种线性双折射的从头算研究，如气相和纯液相中的乙腈所示。使用与时间相关的Kohn-Sham密度泛函理论和标准的CAM-B3LYP泛函，计算了相关的一阶属性以及线性，二次和三次频率相关的响应函数。在液相中，选择了一系列室温（293.15 K）分子动力学快照，为其在632.8 nm的光波长下获得的可观测值的平均值。计算的双折射是针对电磁场的，该磁场对应于T. Roth和GLJA Rikken先前在实验室中使用的实验室设置。物理 莱特牧师 ，2000，85，4478.在这些条件下，乙腈被示出为表现出弱琼斯响应实际上比检测在测量上面提到的所用的装置的极限更小的大致6.5倍。与相应的气相结果进行比较，并对可测量性指标进行评估，以估算实际测量中三种双折射的重叠程度。对于乙腈，该指数分别比甲基环戊二烯基-Mn-三羰基和环己二烯基-Fe-三羰基分别大3.6和6.7倍。莱特牧师 ，2000，85，4478到表现出强的琼斯信号。