First-principles study of large-amplitude dynamic Jahn-Teller effects in vanadium tetrafluoride

Area of Science:

• Quantum Chemistry
• Molecular Spectroscopy
• Solid State Physics

Background:

• Transition metal tetrahalides possess high symmetry but lack extensive spectroscopic data.
• Jahn-Teller (JT) effects are known to distort highly symmetric molecules.
• Previous JT theory models are limited in describing large-amplitude molecular dynamics.

Purpose of the Study:

• Investigate the electronic potential energy functions of vanadium, niobium, and tantalum tetrafluorides (VF4, NbF4, TaF4).
• Explore the Jahn-Teller distortions in the ground (2E) and excited (2T2) states of these molecules.
• Develop and apply advanced JT Hamiltonians to study molecular dynamics and vibronic spectra.

Main Methods:

• Performed ab initio calculations of electronic potential energy functions.
• Constructed higher-order Jahn-Teller Hamiltonians using symmetry-adapted nuclear displacement coordinates.
• Employed multi-configuration electronic structure methods to determine Hamiltonian coefficients.
• Computed vibronic spectra using the developed large-amplitude JT Hamiltonians.

Main Results:

• Confirmed strong E × e and T2 × e Jahn-Teller distortions in VF4, NbF4, and TaF4 ground and excited states.
• Identified weaker T2 × t2 JT effects in the 2T2 state.
• Calculated vibronic spectra of VF4, revealing fluxional nonadiabatic dynamics due to strong JT couplings.
• Observed significant inter-mode coupling effects in the vibronic spectrum, deviating from independent-mode approximations.

Conclusions:

• The study provides the first ab initio investigation of dynamical Jahn-Teller effects in VF4.
• Advanced JT Hamiltonians are crucial for accurately describing large-amplitude dynamics in these systems.
• The findings highlight the complex interplay of electronic and nuclear motions in transition metal tetrahalides.