Author Topic: singlet excited state geometry optimization  (Read 7471 times)

administrador.ccc

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singlet excited state geometry optimization
« on: February 09, 2007, 07:11:13 am »
I am performing a B3LYP first singlet excited state geometry
optimization, symmetry a, tzvp basis set. The work made some
optimization steps but it stops with error:

reference state is non-real unstable
egrad ended abnormally

Taking the last coord file (or even the previous coord file) and
starting a job from scratch, I got the same error.

dimi

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Re: singlet excited state geometry optimization
« Reply #1 on: February 21, 2007, 09:55:00 am »
Hello,

the message "reference state is non-real unstable" means that the ground state solution is not stable with respect to KS orbitals becoming complex. Usually, this is an indication for a conical intersection between the ground state and some excited state at the given geometry. Your can also see it from the excitation energy becoming really small (<0.1 eV or so). In that case there is basically no remedy to this problem since it just represents the shape of the potential energy surface.

Dmitrij

methane

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Re: singlet excited state geometry optimization
« Reply #2 on: March 11, 2007, 10:44:17 pm »
Does this mean the same thing?

 Reference state is unstable
 egrad ended abnormally


turbomaster

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Re: singlet excited state geometry optimization
« Reply #3 on: March 27, 2007, 09:08:01 pm »
I guess so...

Does this mean the same thing?

 Reference state is unstable
 egrad ended abnormally



JakubV

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Re: singlet excited state geometry optimization
« Reply #4 on: April 21, 2016, 04:04:03 pm »
Hello,

I have a similar problem with the triplet T1 excited state energy optimization for uranyl-triauqa-sulphate complex within the DFT/B3LYP/def-SVP (Turbomole V6.5).
I started the calculation from the optimal geometry for the ground S0 state. But soon after the optimalization (26 steps in steepest descent algorithm with dqmax=0.1) I have get the GEO_OPT_FAILED result since the last point has a

" Reference state is unstable
 egrad ended abnormally
"

error message on its end.

My supervisor (who doesn't supervise particularly this project, I am playing with uranyl more like on my own) told me, that it is obvious that the DFT converged to excited state, so I should swap MOs (or KS orbitals to be accurate).

But I am not sure if just reordering the MOs from the failed calculation (or from the last point of the optimization trajectory where it still worked) would work ... and which one of the virtuals I should take instead of the currect HOMO (or HOMO-1, HOMO-2, ?). Since the resulting occupation is 2222...2 00..0. Is it possible to do the swap before the DFT-self-consistent equations are being solved?

I have found elsewhere (https://groups.google.com/forum/#!topic/newtonx/G7DkofJR5YM) answer (for completely different molecule and in combination with the dynamics, but the problem might be the same) that

- Unrestricted KS
(and/or) - Fractional occupation (in particular, temperature smearing)

would work.

Since I am interested in temperature smearing of KS occupation numers also with the perspective to better model 298K temperature effects, I will try the last one.

I will try both the post-DFT reordering