Firstly, the equilibrium geometries of the three molecules in the XALKENEDB dataset, namely ethene (C 2 H 4 ), propene (C 3 H 6 ) and butene (C 4 H 8 ) were determined. Notably, for butene, the geometry of the cis-isomer, which is energetically less favorable than the global minimum structure (trans-butene), was also optimized. The equilibrium geometries were obtained using density functional theory (DFT) by means of the hybrid functional PBE0 in conjunction with the def2-TZVP basis and Grimme-Dispersion with Becke-Johnson damping as implemented in the orca 5.0.3 15 software package. A vibrational analysis was conducted to confirm that the obtained geometries correspond to minima on the potential energy surface.