Fast vibrational configuration interaction using generalized curvilinear coordinates and self-consistent basis

Lauvergnat, David M.; Scribano, Yohann; Benoit, David M.

Abstract

In this paper, we couple a numerical kinetic-energy operator approach to the direct-vibrational self-consistent field (VSCF)/vibrational configuration interaction (VCI) method for the calculation of vibrational anharmonic frequencies. By combining this with fast-VSCF, an efficient direct evaluation of the ab initio potential-energy surface (PES), we introduce a general formalism for the computation of vibrational bound states of molecular systems exhibiting large-amplitude motion such as methyl-group torsion. We validate our approach on an analytical two-dimensional model and apply it to the methanol molecule. We show that curvilinear coordinates lead to a significant improvement in the VSCF/VCI description of the torsional frequency in methanol, even for a simple two-mode coupling expansion of the PES. Moreover, we demonstrate that a curvilinear formulation of the fast-VSCF/VCI scheme improves its speed by a factor of two and its accuracy by a factor of 3.

• Journal Article Type: Article
• Publication Date: Sep 7, 2010
• Journal: JOURNAL OF CHEMICAL PHYSICS
• Print ISSN: 0021-9606
• Electronic ISSN: 1089-7690
• Publisher: AIP Publishing
• Peer Reviewed: Peer Reviewed
• Volume: 133
• Issue: 9
• Article Number: ARTN 094103
• Pages: 094103 - 0
• APA6 Citation: Scribano, Y., Lauvergnat, D. M., & Benoit, D. M. (2010). Fast vibrational configuration interaction using generalized curvilinear coordinates and self-consistent basis. The Journal of chemical physics, 133(9), 094103 - 0. https://doi.org/10.1063/1.3476468
• DOI: https://doi.org/10.1063/1.3476468
• Keywords: Ab initio calculations; Configuration interactions; Librational states; Organic compounds; SCF calculations; Vibrational states; Large-amplitude vibrations; Kinetic-energy operators; Bound-state eigenvalues; Ab initio potential-energy; Grid hamiltonian me