Here we use, the two-state model of Sala et al. with 5 dimensions. The model was extended by a harmonic ground-state PE surface using the ground-state frequencies of the equilibrium geometry. Adiabatic energies are obtained by diagonalization of the diabatic matrix. Adiabatic gradients are calculated by a first-order finite-difference scheme from the adiabatic energies. The model is implemented in the PySurf framework and is included as an example system in the program package as the PyrazineSala Plugin.