“…As a result, 1a structure becomes the only one stable at the MP2/aug-cc-pVTZ level of theory. This structure was also predicted in previous theoretical studies (Makarewicz et al, 1993;Sadlej and Mazurek, 1995;Kieninger and Ventura, 1997;Sadlej et al, 1998;Jena and Mishra, 2005) and confirmed by matrix-isolation infrared (Fredin et al, 1975;Tso and Lee, 1985), molecular beam electric resonance microwave (Peterson and Klemperer, 1984) and optothermal infrared (Block et al, 1992) experiments. The structure of the complex of CO 2 with two water molecules is shown in Fig.…”