Department of Chemistry, Iowa State University, Ames, Iowa 50011, USA
J Phys Chem A. 2009 Nov 19;113(46):12749-53. doi: 10.1021/jp908032x.
Conical intersections (CIs) of ethylene have been successfully determined using spin-flip density functional theory (SFDFT) combined with a penalty-constrained optimization method. We present in detail three structures, twisted-pyramidalized, hydrogen-migrated, and ethylidene CIs. In contrast to the linear response time-dependent density functional theory, which predicts a purely twisted geometry without pyramidalization as the S(1) global minimum, SFDFT gives a pyramidalized structure. Therefore, this is the first correct optimization of CI points of twisted ethylene by the DFT method. The calculated energies and geometries are in good agreement with those obtained by the multireference configuration interaction (MR-CI) method and the multistate formulation of second-order multireference perturbation theory (MS-CASPT2).
使用自旋翻转密度泛函理论（SFDFT）结合罚约束优化方法，成功确定了乙烯的锥形交叉点（CIs）。我们详细介绍了三种结构，扭曲的金字塔形、氢迁移和乙基 CIs。与线性响应含时密度泛函理论相反，后者预测 S(1) 全局最小值为纯扭曲几何形状而没有金字塔化，SFDFT 给出了金字塔化结构。因此，这是通过 DFT 方法对扭曲乙烯的 CI 点进行的首次正确优化。计算出的能量和几何形状与多参考组态相互作用（MR-CI）方法和二阶多参考微扰理论（MS-CASPT2）的多态公式得到的结果非常吻合。
