Calculation of solvent shifts on electronic g-tensors with the conductor-like screening model (COSMO) and its self-consistent generalization to real solvents (Direct COSMO-RS)
Calculation of solvent shifts on electronic g-tensors with the conductor-like screening model (COSMO) and its self-consistent generalization to real solvents (Direct COSMO-RS)
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DOI：
10.1021/jp056016z
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发表时间：
2006-02-16
影响因子：
2.9
通讯作者：
Neese, F
中科院分区：
文献类型：
--
作者：
Sinnecker, S;Rajendran, A;Neese, F
采用类导体筛选模型（COSMO）研究了溶剂对有机自由基电子g值的影响。以已有研究的二苯基一氧化氮和二叔丁基一氧化氮自由基为试验用例。计算采用了不受自旋限制的密度泛函理论和BP和B3LYP密度泛函。g张量计算为对外部磁场和电子磁矩的混合二阶导数性质。通过耦合摄动DFT方法确定了Kohn-Sham轨道对外部磁场的一阶响应。采用精确多中心自旋轨道平均场（SOMF）方法处理自旋轨道耦合算子。假设重要的氢键是通过超分子方法明确建模的，并且基集足够饱和，COSMO计算可以准确预测各向同性g移，相对于实验偏差不超过100 ppm。采用最近发展的自洽COSMO方法对真实溶剂（cosmos - rs）进行修正，得到了非常精确的结果，本文将其简要介绍为直接cosmos - rs （d - cosmos - rs）。该模型在不使用超分子方法的情况下为水提供了类似高精度的各向同性g移。这是一个重要的结果，因为它解决了许多与超分子方法相关的问题，如局部极小值和合适模型系统的选择。因此，自洽d - cosmos - rs将一些特定的溶剂化效应纳入连续统模型，特别是它似乎成功地模拟了氢键的影响。尽管尚未得到广泛证实。这为计算性质开辟了一种新的方法，迄今为止，这种方法只能通过在连续介质溶剂化方法中包含显式溶剂分子来计算。
The conductor-like screening model (COSMO) was used to investigate the solvent influence on electronic g-values of organic radicals. The previously studied diphenyl nitric oxide and di-tert-butyl nitric oxide radicals were taken as test cases. The calculations employed spin-unrestricted density functional theory and the BP and B3LYP density functionals. The g-tensors were calculated as mixed second derivative properties with respect to the external magnetic field and the electron magnetic moment. The first-order response of the Kohn-Sham orbitals with respect to the external magnetic field was determined through the coupled-perturbed DFT approach. The spin-orbit coupling operator was treated using an accurate multicenter spin-orbit mean-field (SOMF) approach. Provided that important hydrogen bonds are explicitly modeled by a supermolecule approach and that the basis set is sufficiently saturated, the COSMO calculations lead to accurate predictions of isotropic g-shifts with deviations of not more than 100 ppm relative to experiment. Very accurate results were obtained by employing a recently developed self-consistent modification of the COSMO method to real solvents (COSMO-RS), which we briefly introduce in this paper as direct COSMO-RS (D-COSMO-RS). This model gives isotropic g-shifts of similar high accuracy for water without using the supermolecule approach. This is an important result because it solves many of the problems associated with the supermolecule approach such as local minima and the choice of a suitable model system. Thus, the self-consistent D-COSMO-RS incorporates some specific solvation effects into continuum models, in particular it appears to successfully model the effects of hydrogen bonding. Although not yet widely validated. this opens a novel approach for the calculation of properties which so far only could be calculated by the inclusion of explicit solvent molecules in continuum solvation methods.