Classical approach based on full-size adiabatic potential energy surfaces to the thermal expansion of the Jahn-Teller molecules. Example of niobium tetrahalides NbX4 (X = Br, I)

Abstract

The methods of CASSCF, the perturbation theory and taking into account relativistic effects were applied to study the structure of NbX4 (X = Br, I) molecules in the ground and excited electronic states. Due to Jahn-Teller distortion of the Td structure, the compressed D2d structure corresponds to minimum on the lower sheet of PES. For 2E ⊗ e Jahn-Teller problem the vibronic Schrödinger equation has been solved in the diabatic basis. The original method was used for the simulation of available gas-phase electron diffraction data. A good agreement between experimental and theoretical results supports the reliability of the theoretical data.