Simultaneous determination of nuclear and electronic wave functions without Born-Oppenheimer approximation: Ab initio NO+MO/HF theory

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We develop a simultaneous determination method of nuclear and electronic wave functions without the Born-Oppenheimer approximation. We examine two expanding methods, namely, molecular orbital (MO)-type and valence bond (VB)-type expansions for a nuclear orbital, which is a one-particle wave function of a nucleus. The VB-type expansion is shown to be more accurate than the MO-type one because of the local nature of the nuclei. We also investigate the basis function expansion of the nuclear orbital and propose a scheme to determine the orbital exponent for the nuclear basis function. Numerical calculations confirm the accuracy and feasibility of the present method.

Original languageEnglish
Pages (from-to)511-517
Number of pages7
JournalInternational Journal of Quantum Chemistry
Issue number6
Publication statusPublished - 2002 Feb 20



  • Ab initio NO+MO/HF theory
  • Non-Born-Oppenheimer theory
  • Nuclear basis function
  • Translation-free Hamiltonian
  • VB-type expansion

ASJC Scopus subject areas

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

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