First-principles studies of Jahn-Teller effects in vanadium, niobium, and tantalum tetrafluoride molecules: electronic structure, vibronic spectra and radiationless decay dynamics
Final Report Abstract
Jahn-Teller (JT) theory has a venerable history of more than 80 years. Despite the wealth of literature on the JT effect, extensions of JT theory are still necessary for accurate theoretical descriptions of spectroscopic and kinetic phenomena in polyatomic molecules and in solidstate materials. In the present project, JT theory was extended beyond the current state of the art to enable first-principles predictions of the vibronic spectra of the tetrahedral transitionmetal tetrafluorides VF4, NbF4 and TaF4. These five-atomic systems were selected as model systems for the further development of theoretical and computational methods. The five-atomic transition-metal tetrahalides are more challenging systems than the four-atomic transition-metal trihalides, but are more amenable to a first-principles theoretical treatment than the seven-atomic octahedral transition-metal complexes. A group-theoretical framework was developed which allows the construction of JT Hamiltonian operators up to arbitrarily high orders in symmetry-adapted nuclear displacements from the tetrahedral reference geometry. This extension of JT theory was combined with accurate ab initio scalar-relativistic multi-configuration self-consistent-field calculations of the energies of the 2E ground state and the 2T2 excited state of VF4, NbF4. From these data, high-order JT Hamiltonians were obtained by a judicious least-squares fitting procedure. With these Hamiltonians, vibronic spectra of the 2E and 2T2 states of VF4 and NbF4 were computed for the first time. While spinorbit (SO) coupling effects are negligible for VF4, they become relevant for NbF4 and, in particular, for TaF4. The effects on SO coupling on the potential-energy surfaces of NbF4 and TaF4 has been systematically explored over a wide range of nuclear geometries by electronicstructure calculations. This joint DFG-RFBR research project served to foster the exchange of ideas, knowledge and computational methods between the two research groups.
Publications
- First-principles study of large-amplitude dynamic Jahn-Teller effects in vanadium tetrafluoride. J. Chem. Phys. 152, 094304 (2020)
K. R. Nandipati, A. O. Vasilyev, I. S. Navarkin, V. G. Solomonik and W. Domcke
(See online at https://doi.org/10.1063/1.5131739) - Strong static and dynamic Jahn-Teller and pseudo-Jahn-Teller effects in niobium tetrafluoride. J. Chem. Phys. (2021)
O. A. Vasilev, K. R. Nandipati, I. S. Navarkin, V. G. Solomonik and W. Domcke
(See online at https://doi.org/10.1063/5.0045905)
