TY - JOUR
T1 - Singlet-triplet energy gap for trimethylenemethane, oxyallyl diradical, and related species
T2 - Single- and multireference computational results
AU - Saito, Toru
AU - Nishihara, Satomichi
AU - Yamanaka, Shusuke
AU - Kitagawa, Yasutaka
AU - Kawakami, Takashi
AU - Yamada, Satoru
AU - Isobe, Hiroshi
AU - Okumura, Mitsutaka
AU - Yamaguchi, Kizashi
N1 - Funding Information:
T. S. is grateful for the Research Fellowships from Japan Society for the Promotion of Science for Young Scientists (JSPS). This work has been supported by Grants-in-Aid for Scientific Research (KAKENHI) (Nos. 21550014, 19750046, 19350070) from JSPS and that on Grant-in-Aid for Scientific Research on Innovative Areas (“Coordination Programming” area 2170, No. 22108515) from the Ministry of Education, Culture, Sports, Science, and Technology (MEXT).
PY - 2011/12
Y1 - 2011/12
N2 - We have investigated the through-bond exchange interactions in three non-Kekulé hydrocarbon diradicals on the basis of single- and multireference coupled cluster and related broken-symmetry (BS) methods. The singlet-triplet energy gap (S-T gap) and diradical characters for these species are evaluated. It is found that the spin contamination involved in the BS solutions is non-negligible and the approximate spin-projection method greatly improves the usual BS solutions. As for Mukherjee's state-specific multireference coupled cluster (MkMRCC) computations, the size-consistent correction with the UHF localized natural orbitals (ULO) is useful to obtain the qualitatively correct 2J values.
AB - We have investigated the through-bond exchange interactions in three non-Kekulé hydrocarbon diradicals on the basis of single- and multireference coupled cluster and related broken-symmetry (BS) methods. The singlet-triplet energy gap (S-T gap) and diradical characters for these species are evaluated. It is found that the spin contamination involved in the BS solutions is non-negligible and the approximate spin-projection method greatly improves the usual BS solutions. As for Mukherjee's state-specific multireference coupled cluster (MkMRCC) computations, the size-consistent correction with the UHF localized natural orbitals (ULO) is useful to obtain the qualitatively correct 2J values.
KW - Broken-symmetry method
KW - Diradical species
KW - Multireference coupled cluster
KW - Spin-projection method
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U2 - 10.1007/s00214-011-0914-z
DO - 10.1007/s00214-011-0914-z
M3 - Article
AN - SCOPUS:81855185280
SN - 1432-881X
VL - 130
SP - 739
EP - 748
JO - Theoretical Chemistry Accounts
JF - Theoretical Chemistry Accounts
IS - 4-6
ER -