Ab initio study of the CO2 dimer and the CO2 ion complexes (CO2)2+ and (CO2)3+

摘要: Ab initio calculations were performed at several levels for neutral CO/sub 2/, 2/ dimer, and the cations (CO/sub 2/)/sub 2//sup +/ 3//sup +/. At highest level, a dimer of C/sub 2h/ symmetry (staggered side-by-side) is bound by 1.3 kcal/mol, which 0.2 kcal/mol more stable than T-shaped (C/sub 2v/ symmetry). The dissociation energy complex calculated to be 16.2 4.4 greater complex. Due smaller amount spin contamination (spin polarization), stability this characterized partial bond between oxygens overestimated (MP4SDQ/6-31G*) level relative ion (plus 2/) have significant contamination. Projecting out largest contaminant PMP2/6-31G* PMP4/3-21G leads an estimated decrease in separation 6.3 (relative method). Two trimers considered, cyclic (C/submore » 3h/) cross-shaped (D/sub 2h/). 2h/) 16.0 with respect monomers. Vibrational frequencies used compute entropies reaction ..-->.. + 2CO/sub +/.« less