| 11:11:49 PM PDT - Wed, Apr 22nd 2020 |
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GAMESS calculations B3LYP RHF using accd all give 4.65eV and 5.13eV, and reference Absorption and Fluorescence Spectra of Uracil in the Gas Phase and in Aqueous Solution: A TD-DFT Quantum Mechanical Study gives TDDFT calculated gaseous n/pi 4.80eV and Pi/Pi 5.26eV.
GAMESS cr-eomccsd(T) with aug-cc-pvdz can give two gaseous peaks of 4.96 and 5.62 eVs, the lowest two among all kinds of the first two calculated, but perhaps not the most accurate ones.
According to the reference:Theoretical Study of the Electronic Spectra of Uracil and Thymine
"The present paper reports the results of a similar study on the pyrimidine bases uracil and thymine. The pi-pi* transitions lowest in energy are predicted to be located at 5.0,5.8, 6.5, and 7.0 eV for uracil. ...In addition, we locate four n-pi* transitions and find the first one to be close in energy to the lowest pi-pi* transition."
Very Best Regards!
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