The calculation of vibrational energy levels of polyatomic molecules including anharmonic effect using contact transformation perturbation method
Article first published online: 30 JUL 2012
Copyright © 2012 Wiley Periodicals, Inc.
International Journal of Quantum Chemistry
Volume 113, Issue 8, pages 1180–1191, 15 April 2013
How to Cite
Dehestani, M. and Kalantari, Z. (2013), The calculation of vibrational energy levels of polyatomic molecules including anharmonic effect using contact transformation perturbation method. Int. J. Quantum Chem., 113: 1180–1191. doi: 10.1002/qua.24232
- Issue published online: 6 MAR 2013
- Article first published online: 30 JUL 2012
- Manuscript Accepted: 21 MAY 2012
- Manuscript Revised: 20 MAY 2012
- Manuscript Received: 14 NOV 2011
- contact transformation perturbation theory;
- anharmonic effect;
- vibrational energy levels
Using contact transformation perturbation method based on the Taylor expansion of the potential energy function in terms of dimensionless normal coordinates up to sixth-order, the vibrational energy levels in terms of force constants are derived. The contact transformation theory has been applied to simplify the calculation of perturbation effects. To calculate the second-order vibrational energy correction, the third and fourth-order terms of potential function have been placed in the first-order perturbation Hamiltonian and the second-order Hamiltonian contains hexatic ones. We present expressions which give relations between the fourth- and sixth-order terms in dimensionless normal coordinates of the potential and the anharmonicity coefficients. For illustration, a set of vibrational energies levels of SO2, and H2O molecules including anharmonic effects has been calculated. © 2013 Wiley Periodicals, Inc.