Under vacuum conditions, we find no single step in either reaction pathway to be exothermic. The initial [CO 3 ] -2 formation step, while endothermic for both paths, required significantly more energy in the case of pathway a) (1.2 eV) compared to b) (0.3 eV). However, the second reaction step almost completely offsets this difference in energetic cost, with a) requiring 0 eV and b) needing 0.8 eV for the epoxide formation reaction. These results so far appear to be rather obvious, as in the absence of any surface for the carbonate to bind to or the reactants to adsorb on, we can expect neither the assumed driving force (the Na 2 CO 3 formation) nor any overall energetic difference between the two reaction pathways, due to both educts having almost the same heat of formation. One aspect that we have neglected within our calculations so far is the influence of the zero-point-energy. While the influence of the zero-point-energy is often neglected because it is comparatively small, it can significantly impact chemical reactions, particularly in which multiple bonds are broken/ created. We performed frequency calculations for the vacuum reaction and were able to confirm that for the reactions in question, the change in zero-point-energy is relatively low, with the most significant change of any reaction step being 0.13 eV and the zero-point-energy influence over the complete PO formation reactions being no higher than 0.03 eV, which is far below the zero-point-energy of a typical C-H bond of 0.2-0.3 eV . Progressing to the surface reactions, we find both exothermic and endothermic reaction steps. A list of all reaction energies is compiled in table . According to our calculations, the carbonate-producing reaction (Step 1) is exothermic on all tested surfaces except the NaCl(100) surface. However, the PO formation step (Step 2) was endothermic on all surfaces except the NaCl(100) surface. In particular, most surfaces did not exhibit a reaction path without at least one step energy over 1 eV.