Ab initio CASSCF and DFT investigations of (H2O)2+ and (H2S)2+: hemi-bonded vs proton-transferred structure

Ghanty, Tapan K. ; Ghosh, Swapan K. (2002) Ab initio CASSCF and DFT investigations of (H2O)2+ and (H2S)2+: hemi-bonded vs proton-transferred structure Journal of Physical Chemistry A, 106 (48). pp. 11815-11821. ISSN 1089-5639

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Official URL: http://pubs.acs.org/doi/abs/10.1021/jp0264275

Related URL: http://dx.doi.org/10.1021/jp0264275


High level ab initio calculations using a complete active space self-consistent field (CASSCF) and multiconfigurational quasi-degenerate perturbation theory (MCQDPT2) methods as well as density functional theory (DFT)-based calculations with different exchange-correlation energy density functionals have been performed for predicting the relative stability of the proton-transferred vs hemi-bonded isomers of (H2O)2+ and (H2S)2+ species. For (H2O)2+, DFT calculation using conventional exchange-correlation functionals predicts the hemi-bonded structure to be the ground state while use of full or half Hartree-Fock exchange and local correlation predicts a higher stability of the proton-transferred structure in agreement with ab initio results. For the (H2S)2+ system, all of the methods lead to the prediction of lower energy for the hemi-bonded isomer. No regular trend of the exchange-correlation energy component with the total energy difference is however observed. Dynamical electron correlation effect incorporated through MCQDPT2 is found to be much stronger in (H2O)2+ as compared to (H2S)2+. An analysis of the nature of interactions involved in the (H2O)2+ and (H2S)2+ systems within the framework of Bader's topological theory of atoms in molecules is also presented through the plots of the Laplacian ∇2ρ of the electron density ρ (r) and also other related quantities at the bond critical points with the objective of rationalizing the relative stability of the two isomers in both (H2O)2+ and (H2S)2+.

Item Type:Article
Source:Copyright of this article belongs to American Chemical Society.
ID Code:11134
Deposited On:09 Nov 2010 03:54
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