论文标题
激发状态的登山策略：用EOM-CC4修改参考值
A Mountaineering Strategy to Excited States: Revising Reference Values with EOM-CC4
论文作者
论文摘要
在小型有机化合物中高度精确的垂直激发能的计算确定框架中，我们探索了依靠大约四阶耦合簇（CC）方法的动作形式主义提供的可能性，CC4。我们证明，使用基于CC（包括四倍体激发）（CCSDTQ）的200多个参考值的扩展集，CC4对激发态的CCSDTQ非常近似，而单个激发的贡献则是平均偏差为$ 0.003 $ $ 0.003 $ ev的单个激发的贡献。接下来，我们评估了几种添加剂集校正方案的准确性，其中使用紧凑的基础集获得的垂直激发能和高阶CC方法通过较大基集进行的低阶CC计算进行校正。尽管它们的准确性显着取决于实际方案，但发现这种策略总体上是非常有益的。最后，使用CC4来改善含有四到六个（非氢）原子的分子的QUEST数据库的几个理论最佳估计，为此，在CCSDT级别计算了先前的估计值。
In the framework of the computational determination of highly-accurate vertical excitation energies in small organic compounds, we explore the possibilities offered by the equation-of-motion formalism relying on the approximate fourth-order coupled-cluster (CC) method, CC4. We demonstrate, using an extended set of more than 200 reference values based on CC including up to quadruples excitations (CCSDTQ), that CC4 is an excellent approximation to CCSDTQ for excited states with a dominant contribution from single excitations with an average deviation as small as $0.003$ eV. We next assess the accuracy of several additive basis set correction schemes, in which vertical excitation energies obtained with a compact basis set and a high-order CC method are corrected with lower-order CC calculations performed in larger basis sets. Such strategies are found to be overall very beneficial, though their accuracy depend significantly on the actual scheme. Finally, CC4 is employed to improve several theoretical best estimates of the QUEST database for molecules containing between four and six (non-hydrogen) atoms, for which previous estimates were computed at the CCSDT level.
