Elongation method at restricted open-shell Hartree-Fock level of theory

Jacek Korchowiec, Feng Long Gu, Yuriko Aoki

    Research output: Contribution to journalArticlepeer-review

    40 Citations (Scopus)


    Elongation and cutoff elongation methods are described at the restricted open-shell Hartree-Fock (ROHF) level of theory. Test calculations are performed for polyethylene radicals CH3-(CH2)N-1 (N = 8, 10, 12, ⋯ 40), using minimal (STO-3G) and valence double-ζ (6-31G) basis sets. It is demonstrated that the process of diminishing the variational space in the elongation method does not introduce a large error, and that the error can be controlled by the size of the starting radical. Implementation of the cutoff technique to the elongation method leads to distinct time savings in the self-consistent field (SCF) process and does not worsen the results. In contrast to full variational space ROHF treatment, the step SCF CPU time in the cutoff elongation calculations appears to saturate to an asymptotic value that permits investigation of large molecular systems.

    Original languageEnglish
    Pages (from-to)875-882
    Number of pages8
    JournalInternational Journal of Quantum Chemistry
    Issue number6
    Publication statusPublished - Dec 20 2005

    All Science Journal Classification (ASJC) codes

    • Atomic and Molecular Physics, and Optics
    • Condensed Matter Physics
    • Physical and Theoretical Chemistry


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