Ab initio study of the CO/sub 2/ dimer and the CO/sub 2/ ion complexes (CO/sub 2/)/sub 2//sup +/ and (CO/sub 2/)/sub 3//sup +/
Ab initio calculations were performed at several levels for neutral CO/sub 2/, CO/sub 2/ dimer, and the cations (CO/sub 2/)/sub 2//sup +/ and (CO/sub 2/)/sub 3//sup +/. At the highest level, a CO/sub 2/ neutral dimer of C/sub 2h/ symmetry (staggered side-by-side) is bound by 1.3 kcal/mol, which is 0.2 kcal/mol more stable than a T-shaped dimer (C/sub 2v/ symmetry). The dissociation energy of a (CO/sub 2/)/sub 2//sup +/ complex of C/sub 2h/ symmetry is calculated to be 16.2 kcal/mol which is 4.4 kcal/mol greater than the dissociation energy of the T-shaped (CO/sub 2/)/sub 2//sup +/ complex. Due to a smaller amount of spin contamination (spin polarization), the stability of this complex which is characterized by a partial bond between oxygens is overestimated at the (MP4SDQ/6-31G*) level relative to the T-shaped ion complex and CO/sub 2//sup +/ (plus CO/sub 2/) which have significant spin contamination. Projecting out the largest spin contaminant at the PMP2/6-31G* level and at the PMP4/3-21G level leads to an estimated decrease in the energy separation between the C/sub 2h/ symmetry complex and the T-shaped complex of 6.3 kcal/mol (relative to the (MP4SDQ/6-31G*) method). Two trimers of (CO/sub 2/)/sub 3//sup +/ were considered, a cyclic complex (C/sub 3h/) and a cross-shaped complex (D/sub 2h/). The more stable (CO/sub 2/)/sub 3//sup +/ complex (D/sub 2h/) is bound by 16.0 kcal/mol with respect to monomers. Vibrational frequencies were used to compute entropies of reaction for (CO/sub 2/)/sub 2//sup +/ ..-->.. CO/sub 2/ + CO/sub 2//sup +/ and (CO/sub 2/)/sub 3//sup +/ ..-->.. 2CO/sub 2/ + CO/sub 2//sup +/.
- Research Organization:
- Auburn Univ., AL
- OSTI ID:
- 6193090
- Journal Information:
- J. Phys. Chem.; (United States), Vol. 91:13
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
54 ENVIRONMENTAL SCIENCES
CARBON DIOXIDE
DISSOCIATION ENERGY
ENTHALPY
ENTROPY
SPECIFIC HEAT
VIBRATIONAL STATES
CALCULATION METHODS
CATIONS
COMPLEXES
DIMERS
IONIZATION POTENTIAL
THEORETICAL DATA
THERMODYNAMICS
CARBON COMPOUNDS
CARBON OXIDES
CHALCOGENIDES
CHARGED PARTICLES
DATA
ENERGY
ENERGY LEVELS
EXCITED STATES
INFORMATION
IONS
NUMERICAL DATA
OXIDES
OXYGEN COMPOUNDS
PHYSICAL PROPERTIES
THERMODYNAMIC PROPERTIES
400201* - Chemical & Physicochemical Properties
500100 - Environment
Atmospheric- Basic Studies- (-1989)