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### RSPCTL WARNING-MAXIMUM NUMBER OF MICROITERATIONS

Posted: **22 Oct 2019, 09:05**

by **ndhieu92**

WIsh you have a good day everyone.

I am trying to calculate for the spin-orbit coupling constant, but I have got a problem. Eventhough the calculation finished without any error, but the result of SOC value between 2 times of calculation is different between each other. Firstly, I checked the input file (mol. and dal. file) and I am sure that it is correct. So I checked the output file and then I always see the warning is: RSPCTL WARNING-MAXIMUM NUMBER OF MICROITERATIONS, 60. So now I am trying to add into dal. file: .MAX MICRO ITERATIONS and increase it into 200. Will this fix my problem? I attached 2 output file and also the new dal.file with my thinking. Please let me know your idea.

Thank you so much

### Re: RSPCTL WARNING-MAXIMUM NUMBER OF MICROITERATIONS

Posted: **23 Oct 2019, 13:55**

by **hjaaj**

Your spin-orbit coupling constants are garbage, because your calculation is triplet unstable (complex eigenvalues in the calculation of lowest triplet excitation). The differences between the two calculations are caused by numerical noise because of the non-convergence.

Either your DFT iterations do not converge to the ground state (do you get same total energy if you try with another program?), or B3LYP is a bad model for this case.

By the way, your ".MAX IT" keyword has no effect because the ".MAX IT" in that place specify the max. number of geometry iterations in a geometry optimization. But it does not help to increase the correct max iterations for response, because the convergence is stuck because of the above mentioned problems.

### Re: RSPCTL WARNING-MAXIMUM NUMBER OF MICROITERATIONS

Posted: **23 Oct 2019, 15:05**

by **ndhieu92**

hjaaj wrote: ↑23 Oct 2019, 13:55

Your spin-orbit coupling constants are garbage, because your calculation is triplet unstable (complex eigenvalues in the calculation of lowest triplet excitation). The differences between the two calculations are caused by numerical noise because of the non-convergence.

Either your DFT iterations do not converge to the ground state (do you get same total energy if you try with another program?), or B3LYP is a bad model for this case.

By the way, your ".MAX IT" keyword has no effect because the ".MAX IT" in that place specify the max. number of geometry iterations in a geometry optimization. But it does not help to increase the correct max iterations for response, because the convergence is stuck because of the above mentioned problems.

Thank you Dr. Hans for your reply. I am sorry but may I ask you a question: Do you mean the SCF energy which was shown in the output file is total energy? And I am thinking to try with another program like molpro to confirm it. I will try to change to MCSCF to see how it works.

### Re: RSPCTL WARNING-MAXIMUM NUMBER OF MICROITERATIONS

Posted: **23 Oct 2019, 15:23**

by **hjaaj**

I mean this final energy:

Code: Select all

`@ Final DFT energy: -2824.469146640524 `

and these final HOMO-LUMO energies:

Code: Select all

```
E(LUMO) : -0.13437205 au (symmetry 1)
- E(HOMO) : -0.14494639 au (symmetry 1)
------------------------------------------
gap : 0.01057434 au
```

Note that the HOMO and LUMO orbital energies are very close, so no wonder there is triplet instability.

### Re: RSPCTL WARNING-MAXIMUM NUMBER OF MICROITERATIONS

Posted: **23 Oct 2019, 16:10**

by **ndhieu92**

hjaaj wrote: ↑23 Oct 2019, 15:23

I mean this final energy:

Code: Select all

`@ Final DFT energy: -2824.469146640524 `

and these final HOMO-LUMO energies:

Code: Select all

```
E(LUMO) : -0.13437205 au (symmetry 1)
- E(HOMO) : -0.14494639 au (symmetry 1)
------------------------------------------
gap : 0.01057434 au
```

Note that the HOMO and LUMO orbital energies are very close, so no wonder there is triplet instability.

Maybe I will try to recalculate with gaussian 09 software with same basis set B3LYP/6-31G* in dal.file to confirm the DFT energy and HOMO-LUMO energies.

I will keep updating the result.

Thank you so much Dr. Hans