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Large vibrational variational calculations using 'multimode' and an iterative diagonalization technique

Handy, N.C. and Carter, S. (2004) Large vibrational variational calculations using 'multimode' and an iterative diagonalization technique. Molecular Physics, 102 (21-22). pp. 2201-2205. ISSN 0026-8976

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To link to this item DOI: 10.1080/00268970410001728870


We have favoured the variational (secular equation) method for the determination of the (ro-) vibrational energy levels of polyatomic molecules. We use predominantly the Watson Hamiltonian in normal coordinates and an associated given potential in the variational code 'Multimode'. The dominant cost is the construction and diagonalization of matrices of ever-increasing size. Here we address this problem, using pertubation theory to select dominant expansion terms within the Davidson-Liu iterative diagonalization method. Our chosen example is the twelve-mode molecule methanol, for which we have an ab initio representation of the potential which includes the internal rotational motion of the OH group relative to CH3. Our new algorithm allows us to obtain converged energy levels for matrices of dimensions in excess of 100 000.

Item Type:Article
Divisions:Life Sciences > School of Chemistry, Food and Pharmacy > Department of Chemistry
ID Code:11317
Uncontrolled Keywords:MOLECULES

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