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Accelerating convergence in the antisymmetric product of strongly orthogonal geminals method

Authors

  • Moto Tarumi,

    1. Department of Chemistry and Biochemistry, School of Advanced Science and Engineering, Waseda University, Tokyo 169-8555, Japan
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  • Masato Kobayashi,

    1. Department of Chemistry and Biochemistry, School of Advanced Science and Engineering, Waseda University, Tokyo 169-8555, Japan
    2. Department of Theoretical and Computational Molecular Science, Institute for Molecular Science, Okazaki 444-8585, Japan
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  • Hiromi Nakai

    Corresponding author
    1. Department of Chemistry and Biochemistry, School of Advanced Science and Engineering, Waseda University, Tokyo 169-8555, Japan
    2. Research Institute for Science and Engineering, Waseda University, Tokyo 169-8555, Japan
    3. CREST, Japan Science and Technology Agency, Tokyo 102-8666, Japan
    • Department of Chemistry and Biochemistry, School of Advanced Science and Engineering, Waseda University, Tokyo 169-8555, Japan
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Abstract

Antisymmetric product of strongly orthogonal geminals (APSG) method is a wavefunction theory that can effectively treat the static electron correlation using two-electron wavefunctions, called geminals. However, the APSG method has the problem of slow convergence in the optimization of the geminal function. In this study, we introduced the direct inversion in the iterative subspace (DIIS) method, for both closed- and open-shell systems, for accelerating its convergence. Two types of error vectors, that is, unitary transformation and orbital gradient, were examined for the DIIS procedure. Numerical assessments revealed that the orbital-gradient error vector shows better performance than the unitary-transformation one. © 2012 Wiley Periodicals, Inc.

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