High level ab initio and density functional theory calculations of the dissociation energies, ionization energies, geometrical variations, and vibrational modes of ground and excited CO2, CO2+, and CO22+

Abstract

AbstractThe potential energy surface of CO22+ ( 3Σg−) is investigated with HF, MP2, MP4, CBS‐Q, G1, G2MP2, G2, G3B3, and B3LYP/6‐311++G(3df,3pd) methods. Density functional theory shows the lowest dissociation channel of this compound to be the formation of CO+ ( 2Σ+)+O+ ( 4Su) and to have a barrier of around 2 eV as well as a dissociation energy of around −3.2 eV. Thus we propose that with enough correlation it is possible to accurately predict the energies of dissociation and barrier widths and heights to test for the stability of a particular molecular species. We also propose a refinement of current understanding by observing HOMO–LUMO gaps, Lowdin and Mulliken bond orders (to test for bond orbital overlap and hence qualitatively describe bonding and fragmentation in these complexes) and predicted spectrum for such studies as ZEKE spectroscopy (to study cationic states) and REMPI (to study the first excited states) of these class of molecules and, we hope, provide future insight into larger and more interesting systems. © 2001 John Wiley & Sons, Inc. Int J Quantum Chem, 2001