標題: | The elusive excited states of bithiophene: a CASPT2 detective story |
作者: | Andrzejak, Marcin Witek, Henryk A. 應用化學系 應用化學系分子科學碩博班 Department of Applied Chemistry Institute of Molecular science |
關鍵字: | Excited states;Bithiophene;CASSCF;CASPT2;Vertical excitation energies;Absorption spectrum |
公開日期: | 1-May-2011 |
摘要: | A systematic multi-reference perturbation theory investigation of the excitation energies and oscillator strengths for the lowest excited states of 2,2'-bithiophene unequivocally shows that its optical spectrum is produced by two (1) B (u) states separated from each other by approximately 1 eV. This picture is confirmed by additional calculations with alternative quantum chemical methods. Our findings are in strong contrast with the previous CASPT2 results of Rubio et al. [J Chem Phys 102:3580 (1995) and Chem Phys Chem 4:1308 (2003)], who predicted that the two lowest (1) B (u) states are quasi-degenerate. The methodological reasons responsible for the previous seemingly erroneous assignment of the optical spectrum of bithiophene are identified and explained in terms of unusually large coupling between the (1) B (u) states introduced by dynamical correlation effects. A general discussion of applicable computational techniques is offered aiming at avoiding similar problems for other molecular systems. |
URI: | http://dx.doi.org/10.1007/s00214-011-0916-x http://hdl.handle.net/11536/8954 |
ISSN: | 1432-881X |
DOI: | 10.1007/s00214-011-0916-x |
期刊: | THEORETICAL CHEMISTRY ACCOUNTS |
Volume: | 129 |
Issue: | 2 |
起始頁: | 161 |
結束頁: | 172 |
Appears in Collections: | Articles |
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