Deriving the Vibronic Coupling Constants of the Cyclopentadienyl Radical with Density Functional Theory and G0W0
<div>The vibronic coupling constants of the cyclopentadienyl radical have been calculated with G<sub>0</sub>W<sub>0</sub>, HF, and DFT with various exchange-correlation functionals. The vibronic coupling constants for HF and DFT were derived using the gradients of the eigenvalues of the degenerate HOMOs of the closed-shell cyclopentadienyl anion, while the gradients of the corresponding quasiparticle energy levels were used in the case of G<sub>0</sub>W<sub>0</sub>. The differences between the linear vibronic constants obtained using HF and DFT were found to be small, and reduced further when the G<sub>0</sub>W<sub>0</sub> correction is applied to HF and DFT. Finally, the linear vibronic coupling constants calculated with G<sub>0</sub>W<sub>0</sub> were found to agree well with the values obtained using high level wave function methods in the literature, which suggests that G<sub>0</sub>W<sub>0</sub> can be a useful tool towards the study of vibronic coupling.</div>