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Re: Can Dalton calculate oscillator strength

Posted: 27 Jul 2020, 07:02
by xiongyan21
One functional in GAMESS modified for ionization potential calculation, contributed last year by Dr. Gerasimov, in A.N.Nesmeyanov Institute of Organoelement Compounds of Russian Academy of Sciences, can give the third one in water, with multireference and charge transfer characters according to the calculation, 0.12eV deviating from the detection wavelength in reference mentioned above. Perhaps it is not the maximum absorption wavelength.
Previously, the second excited state of gaseous uracil, also a hard one, can be described by this functional.
The other functional gives less than 0.3eV error of the third one, also of charge transfer character, when compared with the detection wavelength in the reference, whereas the oscillator strengths of the first two are also very small.

The optimization using Dalton2018 with b3lyp and 6-31+G* has been finished, and 6-31++G(d,p) optimization with that also has been completed.

Very Best Regards!

Re: Can Dalton calculate oscillator strength

Posted: 28 Jul 2020, 09:09
by xiongyan21
During the aug-cc-pvdz and b3lyp calculation of the above using 6-311++G(d,p) with b3lyp optimized geometry, at the beginnning of the DFT response employing Dalton2018, there is a warning
********* WARNING ORBDIA ***********
DIAGONAL ORBITAL HESSIAN HAS 1 NEGATIVE ELEMENTS
...
Perhaps .INA setting is not very suitable.

The result is completely wrong
...
@ Excited state no: 1 in symmetry 1 ( A ) - singlet excitation
-------------------------------------------------------------------

@ Excitation energy : 4.54909991E-02 au
@ 1.2378731 eV; 9984.1202 cm-1; 119.43660 kJ / mol

@ Total energy : -679.67677 au

@ Operator type: XDIPLEN
@ Oscillator strength (LENGTH) : 0.24231228 (Transition moment : 2.8266406 )

@ Operator type: YDIPLEN
@ Oscillator strength (LENGTH) : 2.23750730E-02 (Transition moment : 0.85894454 )

@ Operator type: ZDIPLEN
@ Oscillator strength (LENGTH) : 2.78751923E-03 (Transition moment : -0.30317391 )

...

Very Best Regards!

Re: Can Dalton calculate oscillator strength

Posted: 29 Jul 2020, 06:01
by xiongyan21
An article in China suggested that it has two maximum wavelengths at 204 and 265 nm in 70% hexane, and said the area of the first one is very large, using Shimadzu LC-20AD.
According to the GAMESS calculations, the second functional can give an excitation energy of charge transfer in water with 0.18eV deviating from that, and b3lyp can give two weak peaks deviating from the other by 0.13 and 0.24 eVs, respectively, whose oscillator strengths ranging from around 0.08 to 0.05 and whose transition moments cannot be called small, perhaps together giving the wide, not high peak.
The calculation of the first excited state of this compound is too hard for lots of common functionals because of the tangled multireference and charge transfer properties together.


This pesticide is unusual in that it requires different functionals to characterize its absorptions because of their different natures, making the quantum chemical calculation of pesticldes very amusing, suggested by preliminary studies.


The small imainary frequency during b3lyp Hessian analysis should be eliminated and perhaps the employment of 6-311++G(2d,2p) will do especially considering 6-311++G(2d,2p) b3lyp optimized oxirane exhibits the first frequency of around 58 cm-1, not an imaginary one. I will try.

Very Best Regards!

Re: Can Dalton calculate oscillator strength

Posted: 01 Aug 2020, 00:27
by xiongyan21
The 6-311++G(2d,2p) B3lyp frequency analysis with GAMESS has no imaginary frequency and no warning, meaning a true minimum obtained on the PES, which was first through Monte Carlo search. That is good because it seems the optimization is not easy.
I have used RHF and 6-31++G** to calculate ECD by Dalton2018 , but the third one, with oscillator strength around 0.45, is significant deviating form the experimental value, and velocity, length and London of rotational strength are all negative values ranging from around -47 to -50.

Has Dalton evolved to surpass the calculation of pi-pi* and sigma-pi* for ECD, or are the lengths and velocities correct even if the excitation energies have large discrepencies when compared with experimental ones?


Very Best Regards!

Re: Can Dalton calculate oscillator strength

Posted: 03 Aug 2020, 10:53
by xiongyan21
CAS 864237-81-0, a pesticide, is difficult to optimize, because it requires a lot of Monte Carlo search steps, and the final geometry is obtained using 6-311++G(2d,2p) and B3lyp, all with GAMESS. The excitation energies calculated in water using B3lyp, despite the default grids are questionable, which does not significantly affect final results, can reasonably be compared with the UV spectra obtained by Shimadzu-SPD, etc. in an article published in China, except for the maximum absorption of 200 nm, which is also of multireference character and perhaps charge transfer nature. There is a terrace in the spectra, and the calculation shows three peaks around there where two of them are very weak. The oscillator strength of the first one is small but one direction transition moment is not tiny. The Hessian shows no imaginary frequency of the geometry found with 6-311++G(2d,2p) at RHF level. These should be carefully further studied. If possible, I will also use Dalton2018 to study whether the two softwares can agree.

Very Best Regards!