We implemented CNEO-DFT as well as its analytic gradients with the epc17-1 and epc17-of the PySCF 38,39 package. All ab initio DFT and CNEO-DFT calculations were carried out with the modified PySCF package. Geometry optimization was performed through an interface between the PySCF package and the Atomic Simulation Environment (ASE) package. For each molecule, harmonic vibrational analysis was carried out based on the optimized geometric structure.