Ab initio studies of Osub2/subsup−/sup(Hsub2/subO)subin/i/sub and Osub3/subsup−/sup(Hsub2/subO)subin/i/sub anionic molecular clusters, in/i≤12

摘要

An ab initio study of gaseous clusters of O₂− and O₃− withwater is presented. Based on thorough scans of configurational space, wedetermine the thermodynamics of cluster growth. The results are in goodagreement with benchmark computational methods and existing experimentaldata. We find that anionic O₂−(H₂O)_n and O₃−(H₂O)_nclusters are thermally stabilized at typical atmospheric conditions for atleast n = 5. The first 4 water molecules are strongly bound to the aniondue to delocalization of the excess charge while stabilization of more than 4H₂O is due to normal hydrogen bonding. Although clustering up to 12H₂O, we find that the O₂ and O₃ anions retain at least ca. 80 %of the charge and are located at the surface of the cluster. The O₂−and O₃− speicies are thus accessible for further reactions.We consider the distributions of cluster sizes as function of altitude beforefinally, the thermodynamics of a few relevant cluster reactions are considered.