The PESs for the TSH dynamics are obtained by applying the linear vibronic coupling (LVC) model. The LVC potential is based on three approximations: i) the harmonic oscillator approximation, ii) the LVC approximation, meaning that the vibronic coupling elements depend linearly on normal mode coordinates, and iii) the approximation of taking all excited-state vibrational frequencies to be equal to those corresponding to the ground-state. The LVC parameters were determined by density functional theory (DFT) and time-depentent DFT (TD-DFT) calculations performed at the singlet ground-state ( 1 GS) equilibrium geometry and geometries displaced by ∆q i = ±0.5 with q i being the dimensionless mass-frequency weighted normal mode coordinate for mode i.