A Parameterized Vibronic Spin-Orbit Coupling Model Protocol Suitable for Spectroscopy

Abstract

A diabatization protocol constructing vibronic model Hamiltonians with inclusion of spin-orbit coupling was implemented in Python. This protocol has been extended to include spectroscopic applications. GAMESS package GMC-QDPT level of theory calculations carries out a proposed diabatization scheme to automatically compute a grid of diabatic states in expansions of displaced nuclear coordinates. Diabatic potential energy surfaces can subsequently be constructed through fitting parameters. Generated vibronic models can be used for input to quantum dynamical simulation approaches such as MCTDH and VECC alike, where auto and cross-correlation functions can be obtained after propagation. Simulated gas-phase photoelectron spectra were reproduced for H2O, NH3, and PH3, with excellent agreement to experimentally recorded spectra. Absorption spectra of transition metal trifluorides CoF3 and RhF3, along with iron pentacarbonyl Fe(CO)5, were studied with a triple zeta polarized Sapporo basis set. Both CoF3 and RhF3 showed pronounced splitting originating from spin-orbit coupling effect, whereas Fe(CO)5 only displayed minimal change due to spin-orbit coupling limited to its truncated constant-order spectrum. It is predicted that the Jahn-Teller effect plays a more dominant role over spin-orbit coupling in our Fe(CO)5 model simulated spectra. Streamlining of the protocol has increased its accuracy and robustness, in the interest of supporting future vibronic spin-orbit coupling model research.