Departamento de Química, Universidad Autónoma Metropolitana, México DF, México.
J Phys Chem A. 2011 May 5;115(17):4406-15. doi: 10.1021/jp1095272. Epub 2011 Apr 7.
On the basis of a density-based quantification of the steric effect [Liu, S. B. J. Chem. Phys.2007, 126, 244103], the origin of the internal rotation barrier between the eclipsed and staggered conformers of ethane is systematically investigated in this work from an information-theoretical point of view by using the Fisher information measure in conjugated spaces. Two kinds of computational approaches are considered in this work: adiabatic (with optimal structure) and vertical (with fixed geometry). The analyses are performed systematically by following, in each case, the conformeric path by changing the dihedral angle from 0 to 180° . This is calculated at the HF, MP2, B3LYP, and CCSD(T) levels of theory and with several basis sets. Selected descriptors of the densities are utilized to support the observations. Our results show that in the adiabatic case the eclipsed conformer possesses a larger steric repulsion than the staggered conformer, but in the vertical cases the staggered conformer retains a larger steric repulsion. Our results verify the plausibility for defining and computing the steric effect in the post-Hartree-Fock level of theory according to the scheme proposed by Liu.
基于位阻效应的密度定量[Liu, S. B. J. Chem. Phys.2007, 126, 244103]，本文从信息论的角度，通过共轭空间中的 Fisher 信息测度，系统地研究了乙烷的交叉式和重叠式构象之间的内旋转势垒的起源。这项工作考虑了两种计算方法：绝热（最优结构）和垂直（固定几何）。在每种情况下，我们都通过改变二面角从 0 度到 180 度来沿着构象路径进行分析。这是在 HF、MP2、B3LYP 和 CCSD(T)理论水平和几个基组上计算的。选择密度的描述符来支持观察结果。我们的结果表明，在绝热情况下，交叉式构象的位阻排斥作用大于重叠式构象，但在垂直情况下，重叠式构象仍然具有较大的位阻排斥作用。我们的结果验证了根据刘提出的方案在 Hartree-Fock 后理论水平定义和计算位阻效应的合理性。
