Vasilyev Oleg A, Nandipati Krishna R, Navarkin Ilya S, Solomonik Victor G, Domcke Wolfgang
Department of Physics, Ivanovo State University of Chemistry and Technology, 153000 Ivanovo, Russia.
Theoretical Chemistry, Institute of Physical Chemistry, University of Heidelberg, D-69120 Heidelberg, Germany.
J Chem Phys. 2021 Mar 28;154(12):124305. doi: 10.1063/5.0045905.
We present a first-principles study of the static and dynamic aspects of the strong Jahn-Teller (JT) and pseudo-JT (PJT) effects in niobium tetrafluoride, NbF, in the manifold of its electronic ground state, E, and its first excited state, T. The complex topography of the full-dimensional multi-sheeted adiabatic JT/PJT surfaces is analyzed computationally at the complete-active-space self-consistent-field (CASSCF) and multireference second-order perturbation levels of electronic structure theory, providing a detailed characterization of minima, saddle points, and minimum-energy conical intersection points. The calculations reveal that the tetrahedral (T) configuration of NbF undergoes strong JT distortions along the bending mode of e symmetry, yielding tetragonal molecular structures of D symmetry with T → D stabilization energies of about 2000 cm in the X̃E state and about 6400 cm in the ÃT state. In addition, there exists strong X̃E-ÃT PJT coupling via the bending mode of t symmetry, which becomes important near the crossing seam of the X̃E and ÃT potential energy surfaces. A five-state five-mode JT/PJT vibronic-coupling Hamiltonian is constructed in terms of symmetry-invariant polynomial expansions of the X̃E and ÃT diabatic potential energy surfaces in the e and t bending coordinates. The parameters of the Hamiltonian are determined by a least-squares fit of its eigenvalues to the CASSCF ab initio data. The vibronic spectra and the time evolution of adiabatic electronic population probabilities are computed with the multi-configuration time-dependent Hartree method. The complexity of the spectra reflects the effects of the exceptionally strong E × e and T × e JT couplings and (E + T) × (e + t) PJT coupling. The time evolution of the populations of the adiabatic electronic states after the initial preparation of the ÃT state reveals the femtosecond nonadiabatic dynamics through a multidimensional seam of conical intersection. These results represent the first study of the static and dynamical JT/PJT effects in the X̃E and ÃT electronic states of NbF.
我们对四氟化铌（NbF₄）在其电子基态E及其第一激发态T的多重态中的强 Jahn-Teller（JT）和赝 Jahn-Teller（PJT）效应的静态和动态方面进行了第一性原理研究。在完全活性空间自洽场（CASSCF）和电子结构理论的多参考二阶微扰水平上，通过计算分析了全维多层绝热 JT/PJT 表面的复杂地形，详细表征了极小值、鞍点和最小能量锥形交点。计算结果表明，NbF₄ 的四面体（T）构型沿 e 对称性的弯曲模式经历强烈的 JT 畸变，在 X̃E 态产生 D 对称性的四方分子结构，T→D 稳定能约为 2000 cm⁻¹，在 ÃT 态约为 6400 cm⁻¹。此外，通过 t 对称性的弯曲模式存在强的 X̃E - ÃT PJT 耦合，这在 X̃E 和 ÃT 势能面的交叉缝附近变得很重要。根据 X̃E 和 ÃT 绝热势能面在 e 和 t 弯曲坐标中的对称不变多项式展开，构建了一个五态五模 JT/PJT 振动耦合哈密顿量。哈密顿量的参数通过将其本征值与 CASSCF 从头算数据进行最小二乘拟合来确定。使用多组态时间相关哈特里方法计算了振转光谱和绝热电子布居概率的时间演化。光谱的复杂性反映了异常强的 E×e 和 T×e JT 耦合以及（E + T）×（e + t）PJT 耦合的影响。在初始制备 ÃT 态后，绝热电子态布居的时间演化通过多维锥形交点缝揭示了飞秒非绝热动力学。这些结果代表了对 NbF₄ 的 X̃E 和 ÃT 电子态中静态和动态 JT/PJT 效应的首次研究。
