First-principles studies of Jahn-Teller effects in vanadium, niobium, and tantalum tetrafluoride molecules: electronic structure, vibronic spectra and radiationless decay dynamics

过渡金属四卤化物是一类非常对称的分子，其光谱数据非常少。探索性从头计算的电子势能函数提供的证据表明，钒，铌和钽的四氟化物表现出非常强的Jahn-Teller效应在其电子基态以及在其第一激发电子态。此外，基态表面的上层与激发态表面的下层之间存在圆锥相交缝。Jahn-Teller哈密顿量对这些多片多维势能面的解析表示需要后者理论的发展超越当前的最新技术水平。本项目的目的是利用多组态Hartree-Fock和多参考组态相互作用方法，包括自旋轨道耦合的第一性原理构建标题化合物的高级Jahn-Teller哈密顿量。使用这些Jahn-Teller哈密顿量，电子基态的振动光谱和激发态的电子光谱将被计算。利用含时量子动力学方法研究了激发态通过与基态的伪Jahn-Teller耦合的无辐射失活的时间尺度。这些详细的理论预测可能会刺激未来的实验研究的光谱学和电子物理学的过渡金属四卤化物。

Transition-metal tetrahalides are a vast class of highly symmetric molecules for which very few spectroscopic data exist. Exploratory ab initio calculations of electronic potential-energy functions have provided evidence that the tetrafluorides of vanadium, niobium and tantalum exhibit exceptionally strong Jahn-Teller effects in their electronic ground state as well as in their first excited electronic state. In addition, there exist seams of conical intersection of the upper sheet of the ground-state surface with the lower sheet of the excited-state surface. The analytic representation of these multi-sheeted multi-dimensional potential-energy surfaces by Jahn-Teller Hamiltonians requires the development of the theory of the latter beyond the current state of the art. This project aims at the first-principles construction of advanced Jahn-Teller Hamiltonians for the title compounds, using multi-configuration Hartree-Fock and multireference configuration interaction methods with inclusion of spin-orbit coupling. Using these Jahn-Teller Hamiltonians, vibrational spectra of the electronic ground state and electronic spectra of the excited state will be calculated. The timescale of the radiationless deactivation of the excited state via pseudo-Jahn-Teller coupling with the ground state will be explored with time-dependent quantum dynamics methods. These detailed theoretical predictions may stimulate future experimental investigations of the spectroscopy and photophysics of transition-metal tetrahalides.