标题： 关于视网膜质子化席夫碱模型的准确性 显示英文标题

标题： On the accuracy of retinal protonated Schiff base models

摘要： 我们使用扩展的多态完全活性空间二阶微扰理论（XMS-CASPT2）研究了气相中视黄醛质子化席夫碱模型的基态以及基态与第一激发态之间的最小能量锥形交叉点（MECIs）的分子几何结构。 这项工作中最大的模型是视紫红质发色团在{\epsilon }和{\delta }碳原子之间截断的模型，它由54个原子和12轨道的{\pi }共轭组成。 结果与通过状态平均的完全活性空间自洽场（SA-CASSCF）获得的结果进行了比较。 XMS-CASPT2 的结果表明，与所谓的13-14异构化相关的最小能量锥形交叉点在热力学上不可达，这与 SA-CASSCF 的结果相反。 由 SA-CASSCF 和 XMS-CASPT2 计算得到的锥形交叉点几何结构之间的差异归因于电荷转移态比双自由基态更受动态电子相关作用的稳定。 还考察了不同活性空间、基组和状态平均方案的影响。 显示英文摘要

摘要： We investigate the molecular geometries of the ground state and the minimal energy conical intersections (MECIs) between the ground and first excited states of the models for the retinal protonated Schiff base in the gas phase using the extended multistate complete active space second-order perturbation theory (XMS-CASPT2). The biggest model in this work is the rhodopsin chromophore truncated between the {\epsilon} and {\delta} carbon atoms, which consists of 54 atoms and 12-orbital {\pi} conjugation. The results are compared with those obtained by the state-averaged complete active space self-consistent field (SA-CASSCF). The XMS-CASPT2 results suggest that the minimum energy conical intersection associated with the so-called 13-14 isomerization is thermally inaccessible, which is in contrast to the SA-CASSCF results. The differences between the geometries of the conical intersections computed by SA-CASSCF and XMS-CASPT2 are ascribed to the fact that the charge transfer states are more stabilized by dynamical electron correlation than the diradicaloid states. The impact of the various choices of active spaces, basis sets, and state averaging schemes is also examined.