Ab initio calculation of electronic circular dichroism fortrans-cyclooctene using London atomic orbitals |
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Authors: | Keld L Bak Aage E Hansen Kenneth Ruud Trygve Helgaker Jeppe Olsen Poul Jørgensen |
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Institution: | (1) Department of Physical Chemistry, Copenhagen University, DK-2100 Copenhagen Ø, Denmark;(2) Department of Chemistry, University of Oslo, Blindern, N-0315 Oslo, Norway;(3) Theoretical Chemistry, Chemical Centre, University of Lund, P.O. Box 124, S-22100 Lund, Sweden;(4) Department of Chemistry, Aarhus University, DK-8000 Aarhus C, Denmark |
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Abstract: | Summary The second-quantization magnetic dipole operator that arises when London atomic orbitals are used as basis functions is derived. In atomic units, the magnetic dipole operator is defined as the negative of the first derivative of the electronic Hamiltonian containing the interaction with the external magnetic field. It is shown that for finite basis sets, the gauge origin dependence of the resulting magnetic dipole operator is analogous to that of the exact operator, and that the derived operator converges to the exact operator in the limit of a complete basis set. It is also demonstrated that the length expression for the rotatory strength in linear response calculations gives gauge-origin-independent results. Sample calculations ontrans-cyclooctene and its fragments are presented. Compared to conventional orbitals, the basis set convergence of the rotatory strengths calculated in the length form using London atomic orbitals is favourable. The rotatory strength calculated fortrans-cyclooctene agrees nicely with the corresponding experimental circular dichroism spectrum, but the spectra for the fragment molecules show little resemblance with that oftrans-cyclooctene.Dedicated to Prof. Jan Linderberg |
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Keywords: | Electronic circular dichroism Trans-cyclooctene London atomic orbitals |
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