Torsional barriers and equilibrium angle of biphenyl: Reconciling theory with experiment
Torsional barriers and equilibrium angle of biphenyl: Reconciling theory with experiment
复制标题
DOI：
10.1021/ct800182e
复制
发表时间：
2008-09-01
影响因子：
5.5
通讯作者：
Olsen, Jeppe
中科院分区：
文献类型：
--
作者：
Johansson, Mikael P.;Olsen, Jeppe
结合偶联簇理论和密度泛函理论研究了联苯中两个苯基的内旋势。首次准确再现了实验屏障；我们估计平面构象和垂直构象周围的势垒分别为8.0和8.3 kJ/mol。使用至少增广四倍zeta质量的柔性基集是一个至关重要的先决条件。此外，为了最终使理论与实验相一致，基集向基集极限的外推和电子相关向全构型相互作用极限的外推都是必要的。通过自由能修正，扭转角的最小值明显增大，与实验结果一致。密度泛函B3LYP方法与最高水平的从头算结果相比表现良好。
The barriers of internal rotation of the two phenyl groups in biphenyl are investigated using a combination of coupled cluster and density functional theory. The experimental barriers are for the first time accurately reproduced; our best estimates of the barriers are 8.0 and 8.3 kJ/mol around the planar and perpendicular conformations, respectively. The use of flexible basis sets of at least augmented quadruple-zeta quality is shown to be a crucial prerequisite. Further, to finally reconcile theory with experiment, extrapolations of both the basis set toward the basis set limit and electron correlation toward the full configuration-interaction limit are necessary. The minimum of the torsional angle is significantly increased by free energy corrections, which are needed to reach an agreement with experiment. The density functional B3LYP approach is found to perform well compared with the highest level ab initio results.