What causes the warnings in one kind of ECD calculation but not in another

[hjaaj]

This indicates that you have a so-called singlet instability, which is not seen that often. It means that you can get lower HF energy by using complex orbitals (not implemented in Dalton), similar to that a triplet instability means UHF gives lower energy than RHF.
Conclusion: you need to use MCSCF to get reasonable values.

[xiongyan21]

I have used mp2 natural orbitals for this. Does it exacerbate the situation?

Very Best regards!

[hjaaj]

Your attached output files above are all for HF.
I assume you have performed MCSCF calculations since then, and choosing active space based on MP2 occupation number improve the situation in all calculations I have seen. Note: if two MP2 occupation numbers are close, e.g. 1.974 and 1.977, you should include both, but so accurate is MP2 not. With respect to "close": for the strongly occupied orbitals you should judge from "2 - occupation number", i.e. 0.026 and 0.023 in may example above.

[xiongyan21]

Dear Prof. Jensen
I have only found the DFT example but not the MCSCF input in the test.
Where can I find it?

Very Best Regards!

[xiongyan21]

I used the following input to calculate ECD of the above molecule
**DALTON INPUT
.RUN RESPONSE
**INTEGRALS
.DIPLEN
**WAVE FUNCTION INPUT
.DFT
B3LYP
*SCF INPUT
.MAX DIIS
100
**PROPERTIES
.OPTROT
*ABALNR
.DAMPING
0.0045566
.FREQUENCIES
5
0.050000 0.0525 0.055 0.0575 0.06
**END OF DALTON INPUT

but the program finishes without the intended calculation
| End of Wave Function Section (SIRIUS) |
`---------------------------------------'



.------------------------------------------------.
| Starting in Dynamic Property Section (RESPONS) |
`------------------------------------------------'


------------------------------------------------------------------------------
RESPONSE - an MCSCF, MC-srDFT, DFT, and SOPPA response property program
------------------------------------------------------------------------------


-------- OUTPUT FROM RESPONSE INPUT PROCESSING --------




SCF energy : ...
-- inactive part : ...
-- nuclear repulsion : ...


*****************************************
*** DFT response calculation (TD-DFT) ***
*****************************************


Total CPU time used in RESPONSE: 0.00 seconds
Total wall time used in RESPONSE: 0.00 seconds


.-------------------------------------------.
| End of Dynamic Property Section (RESPONS) |
`-------------------------------------------'

Total CPU time used in DALTON: 5 minutes 28 seconds
Total wall time used in DALTON: 5 minutes 28 seconds

[hjaaj]

Your ECP input does not work because you need .RUN PROPERTIES instead of .RUN RESPONSE to get results from the **PROPERTIES module.

[xiongyan21]

Dear Prof. Jensen
Thanks a lot.
It works for the above molecule. I will recalculate this by the change of frequencies suitable for this molecule and compare the Dalton results with the published theoretical and experimental ones, so that I can calculate that for a pesticide.

Very Best Regards!