************第４２回尾張コンプレックスセミナー*************

Title　：　Theoretical studies on the chemical reactions of diradical
            species by using an approximate spin-projection method

Speaker ：　Toru Saito

Affiliation：　Graduate School of Science, Osaka University

Date　：　Tue. Mar. 29th, 1:30 pm (Almost one hour)

Place　：　Seminar Room (4F),
            Graduate School of Information Science

Abstract：
 The spin-unrestricted Hartree-Fock (UHF) based coupled
cluster singles and doubles (UHF-CCSD) and Mukherjee's state-
specific multireference CCSD (MkCCSD) methods are applied to
several chemical reactions of diradical species. In the case of the
UHF-CCSD method, an approximate spin-projection (AP) method is
applied to the broken-symmetry (BS) singlet solution to remove the
spin contamination.  For several reactions, the stationary points
obtained at the UDFT methods are also corrected by the AP-opt
method.  The present study strongly suggests that the calculated
results are sensitive to the electron correlation and to the spin
contamination even at the CCSD level.  It is also found that the for
diradical systems the AP-UCCSD method well reproduces the
MkCCSD method at lower computational cost. I also find that the
AP correction for the stationary points should be imperative when
the reference triplet state is the ground state. The calculated
results so far and the future trends will be presented in this talk.

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