Calculation of barriers to proton transfer using a variety of electron correlation methods
Article first published online: 19 OCT 2004
Copyright © 1992 John Wiley & Sons, Inc.
International Journal of Quantum Chemistry
Supplement: Proceedings of the International Syposium on Atomic, Molecular, and Condensed Matter Theory and Computational Methods
Volume 44, Issue Supplement 26, pages 817–835, 14/21 March 1992
How to Cite
Luth, K. and Scheiner, S. (1992), Calculation of barriers to proton transfer using a variety of electron correlation methods. Int. J. Quantum Chem., 44: 817–835. doi: 10.1002/qua.560440872
- Issue published online: 19 OCT 2004
- Article first published online: 19 OCT 2004
- Manuscript Received: 11 JUN 1992
The usefulness of various combinations of MCSCF and CI methods in computing correlated proton transfer potentials is investigated for the systems, HF, H7N, H3O, and H5O. MCSCF calculations can accurately determine proton transfer barriers, provided the correlation is limited to the proton transfer process. The proper correlated space can be obtained more easily if the canonical occupied MOs are first subjected to a localization. Various means are tested of including additional electron correlation into the MCSCF methods. CIS and CISD calculations are performed following MCSCF expansion of the wave function using various different MCSCF reference wave functions. The MCSCF + CISD results are excellent, being fairly independent of choice of virtual Mos, although it is important that the occupied orbitals be balanced between the donor and acceptor. Localizing the occupied MOS prior to the MCSCF part of the calculation again results in a further improvement. These results are compared to CI computations using the canonical orbitals (and which are not preceded by MCSCF preparation of the wave function) and to Møller–Plesset results. © 1992 John Wiley & Sons, Inc.