An ab initio investigation on (CO2)n and CO2(Ar)m clusters: geometries and IR spectra

Jose, K. V. Jovan ; Gadre, Shridhar R. (2008) An ab initio investigation on (CO2)n and CO2(Ar)m clusters: geometries and IR spectra The Journal of Chemical Physics, 128 (12). 124310_1-124310_9. ISSN 0021-9606

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An ab initio investigation on CO2 homoclusters is done at MPWB1K/6-31++G(2d) level of theory. Electrostatic guidelines are found to be useful for generating initial structures of (CO2)n clusters. The ab initio minimum energy geometries of (CO2)n with n = 2-8 are T shaped, cyclic, trigonal pyramidal, tetragonal pyramidal, tetragonal bipyramidal, pentagonal bipyramidal, and pentagonal bipyramid with one CO2 molecule attached to it. A test calculation on (CO2)20 cluster is also reported. The geometric parameters of the energetically most favored (CO2)nclusters match quite well their experimental counterparts (wherever available) as well as those derived from molecular dynamics studies. The effect of clustering is quantified through the asymmetric C-O stretching frequency shift relative to the single CO2 molecule. (CO2)n clusters show an increasing blueshift from 1.8 to 9.6 cm-1 on increasing number of CO2 molecules from n = 2 to 8. The energetics and geometries of CO2(Ar)m clusters have also been explored at the same level of theory. The geometries for m = 1-6 show a predominant T type of the argon-CO2 molecule interaction. Higher clusters with m = 7-12 show that the argon atoms cluster around the oxygen atom after the saturation of the central carbon atom. The CO2(Ar)m clusters exhibit an increasing redshift in the C-O asymmetric stretch relative to CO2 molecule of 0.7-5.6 cm-1 with increasing number of argon atoms through m = 1-8.

Item Type:Article
Source:Copyright of this article belongs to American Institute of Physics.
Keywords:Ab Initio Calculations; Infrared Spectra; Molecular Clusters; Red Shift
ID Code:86952
Deposited On:14 Mar 2012 08:01
Last Modified:14 Mar 2012 08:01

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