for the perchlorate decomposition on lithium metal, we observed the reaction of [ClO 4 ] -with sodium metal during an AIMD simulation run in which, similar to the lithium simulations, the chloride atoms stayed in the top layer of the sodium metal, while the oxygen atoms sunk deeper into the surface. This formation of a chloride-rich surface layer represents a significant difference between the perchlorate-free and perchlorate-containing systems. We hypothesize that this formation of a sodium-chloride layer can explain the sudden emergence of PO in the gas phase. To test this hypothesis, we investigated three atomistic properties necessary for detecting PO in our GC measurements, the thermodynamic stability of PO on the respective surfaces, the adsorption energy of PO on a NaCl surface, and the reaction pathway for the formation of PO. We performed AIMD simulations to determine the stability of PO on the sodium-metal / sodium-chloride surface and found that PO follows a ringopening reaction only on the sodium surface.