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大类高度对称的分子，其光谱数据很少。电子势能函数的探索性从头计算提供了证据，证明了钒、铌和钽的四氟化物在它们的电子基态和第一激发电子态都表现出极强的Jahn-Teller效应。此外，基态表面的上片与激发态表面的下片存在锥形相交的缝隙。Jahn-Teller哈密顿对这些多层多维势能表面的解析表示要求后者的理论的发展超出当前的技术水平。本项目旨在利用多组态Hartree-Fock和包含自旋-轨道耦合的多参考组态相互作用方法，构建标题化合物的高级Jahn-Teller哈密顿量的第一性原理。利用这些Jahn-Teller哈密顿量，我们将计算电子基态的振动光谱和激发态的电子光谱。用含时量子动力学方法研究了激发态与基态的伪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激发未来对过渡金属四卤化物的光谱和光物理的实验研究。

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.