C A Valente Daniel, do Casal Mariana T, Barbatti Mario, Niehaus Thomas A, Aquino Adelia J A, Lischka Hans, Cardozo Thiago M
Instituto de Química, Universidade Federal do Rio de Janeiro, Rio de Janeiro, Rio de Janeiro, Brazil.
Aix Marseille University, CNRS, ICR, Marseille, France.
J Chem Phys. 2021 Jan 28;154(4):044306. doi: 10.1063/5.0033272.
Extended quantum chemical calculations were performed for the tetracene dimer to provide benchmark results, analyze the excimer survival process, and explore the possibility of using long-range-corrected (LC) time-dependent second-order density functional tight-biding (DFTB2) for this system. Ground- and first-excited-state optimized geometries, vertical excitations at relevant minima, and intermonomer displacement potential energy curves (PECs) were calculated for these purposes. Ground-state geometries were optimized with the scaled-opposite-spin (SOS) second-order Møller-Plesset perturbation (MP2) theory and LC-DFT (density functional theory) and LC-DFTB2 levels. Excited-state geometries were optimized with SOS-ADC(2) (algebraic diagrammatic construction to second-order) and the time-dependent approaches for the latter two methods. Vertical excitations and PECs were compared to multireference configuration interaction DFT (DFT/MRCI). All methods predict the lowest-energy S conformer to have monomers parallel and rotated relative to each other and the lowest S conformer to be of a displaced-stacked type. LC-DFTB2, however, presents some relevant differences regarding other conformers for S. Despite some state-order inversions, overall good agreement between methods was observed in the spectral shape, state character, and PECs. Nevertheless, DFT/MRCI predicts that the S state should acquire a doubly excited-state character relevant to the excimer survival process and, therefore, cannot be completely described by the single reference methods used in this work. PECs also revealed an interesting relation between dissociation energies and the intermonomer charge-transfer interactions for some states.
对并四苯二聚体进行了扩展量子化学计算，以提供基准结果，分析准分子存活过程，并探索对该体系使用长程校正（LC）含时二阶密度泛函紧束缚（DFTB2）方法的可能性。为此计算了基态和第一激发态的优化几何结构、相关极小值处的垂直激发以及单体间位移势能曲线（PEC）。基态几何结构使用缩放反对称自旋（SOS）二阶莫雷尔-普列斯特定理（MP2）理论、LC-DFT（密度泛函理论）和LC-DFTB2水平进行优化。激发态几何结构使用SOS-ADC(2)（二阶代数图示构建）以及后两种方法的含时方法进行优化。将垂直激发和PEC与多参考组态相互作用DFT（DFT/MRCI）进行了比较。所有方法都预测能量最低的S构象异构体中单体相互平行且相对旋转，能量最低的S构象异构体为位移堆积型。然而，LC-DFTB2在S的其他构象异构体方面存在一些相关差异。尽管存在一些态序反转，但在光谱形状、态特征和PEC方面，各方法之间总体上具有良好的一致性。尽管如此，DFT/MRCI预测S态应具有与准分子存活过程相关的双激发态特征，因此，不能用本工作中使用的单参考方法完全描述。PEC还揭示了某些态的解离能与单体间电荷转移相互作用之间的有趣关系。
