Vitalii | 24 Jun, 2006, 11:46 |
General | (1567 Reads)
Vibronic interactions and symmetry breaking in the 1,4-benzyne radical anion
The 1,4-benzyne radical anion is an example of symmetry breaking system due to a multiconfigurational wavefunction and vibrionic interactions between the ground and a low lying excited state. Most ab initio methods find two energy minima: D2h and C2v, with delocalized and localized charge respectively.
Calculation by HF, DFT, CCSD, CCSD(T), EOM-CC show that energy difference between D2h and C2v minima strongly depends on the amount of correlation energy taken into account. For instance, HF and CCSD place C2v minimum below D2h by 0.971 eV and 0.046 eV, respectively. Higher level theories, EOM-EA-CCSD and CCSD(T), place D2h minimum by 0.071 eV and 0.140 eV below C2v. DFT and EOM-SF-CCSD PES do not have C2v minimum.
Using different geometries, we calculated electron photodetachment spectra for
the C2v and D2h geometries. The comparison with experiment demonstrates that 1,4-benzyne radical anion has D2h symmetry in the ground state, and CCSD describes molecule accurately.
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