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Re^5: Energy rises and oscillate at the end of optimization


Dear All,

First of all, I should note that Ni ion is an open-shell system. Forcing RHF will definitely give wrong results. Probably, this is the reason of poor convergence etc.

Oleg, first of all, you should properly determine the oxidation state of Ni (+2 or +3) and the charge of the ligand (supposedly, 2-). Therefore, the total charge of your complex can be 0 or +1, depending on the charge of the central ion. Anyway, total charge of -1 does not correspond to any realistic oxidation state of Ni ion.

Ni2+ has 8 d electrons (open shell!), and Ni3+ has 7 d electrons (open shell again!). Moreover, this is the open shell with (quasi)degeneration, which precludes from using DFT, even in its Restricted Open-Shell (scftyp=ROHF) or Unrestricted (scftyp=UHF) form. Only State-Averaged CASSCF will do in this case. Search the forum for "MCSCF" or "CASSCF" to find out how to set up CASSCF calculations.

You may use Restricted Open-Shell Hartree-Fock (ROHF) to obtain starting orbitals for CASSCF (never start MCSCF with HUCKEL or HCORE guess!). You should start with the maximum multiplicity (high-spin complex) and reduce it by 2 to see, which multiplicity corresponds to the ground state of this complex.

The fact that you managed to converge the geometry in Priroda means that you converged it to the wrong geometry, which does not make sence. By the way, what were the charge and multiplicity settings in Priroda?

On Fri Sep 12 '14 10:34pm, Oleg Levitskiy wrote
>Thank you, Pavlo!
>Now I've started hessian computation though I don't expect that it will finish soon. Analytical calculation is precluded in this case...

>On Fri Sep 12 '14 5:30am, Pavlo Solntsev wrote
>>Dear Oleg.

>>It looks like you starting geometry very close to a transition state. I would recommend you to calculate hessian first and then perturb imaginary mode if it exists. Then try run optimization starting from exact hessian. Algorithms for transition state search and minimum are similar.

>>Hope this helps.

>>On Thu Sep 11 '14 8:48pm, Oleg Levitskiy wrote
>>>Dear Pavlo,
>>>optimization with corrected parameters did 9 steps and unfortunately almost all of them with energy encrease. It seems that convergence to the predefined gradient value can't be achieved in case of applying solvent modeling as you've supposed...
>>>Nonetheless I attached the resulting out in hope of appearing of any new ideas.

>>>Thanks again,

>>>On Thu Sep 11 '14 5:18am, Pavlo Solntsev wrote
>>>>I would recommend you try these parameters first:
>>>> $contrl scftyp=rhf dfttyp=pbe96
>>>> runtyp=OPTIMIZE icharg=-1 nprint=-5
>>>> maxit=100 ICUT=11      ITOL=30 NZVAR=168 $end
>>>> $system mwords=100 $end
>>>> $SCF DIRSCF=.true. maxdii=20 $end
>>>> $guess guess=moread $end
>>>> $ZMAT DLC=.T. AUTO=.T.$end
>>>> $p2p p2p=.t. dlb=.t. $end
>>>> $basis gbasis=TZV $end
>>>> $PCM PCMTYP=DPCM SOLVNT=input RSOLV=2.155 EPS=35.688 EPSINF=1.806874 $END
>>>> $PCMCAV RIN(58)=1.956 $END

>>>>Before apply a solvent correction, you need to optimize the geometry in a gas phase. Make sure you use a right functional. I am skeptical about pbe96. Do not expect very tight gradient for the geometry with the solvent correction. Usually 10^-4 is ok.

>>>>On Tue Sep 9 '14 3:30pm, Oleg Levitskiy wrote
>>>>>Dear Firefly Users,
>>>>>I've tryed to perform an optimization of anionic complex of Ni (DFT/PBE96, PCM) and faced a problem with convergence. Energy has unexpectedly risen and fluctuate spontaneousely from step to step. I've tryed to increase accuracy (ICUT, ITOL values and also DLCTOL and ORTTOL), to change optimization method (GDIIS, NR), to perform optimization in cartesian or delocalized coordinates, but the result was similar in all cases. Could you advise me something else to solve this problem.
>>>>>The beginning of my input is following:

>>>>> $contrl scftyp=rhf dfttyp=pbe96
>>>>>runtyp=OPTIMIZE icharg=-1 nprint=-5
>>>>>maxit=100 ICUT=20 ITOL=30 NZVAR=168 $end
>>>>> $system kdiag=-1 mwords=100 $end
>>>>> $SCF DIRSCF=.true. maxdii=20 $end
>>>>> $guess guess=moread $end
>>>>> $STATPT method=NR $end
>>>>> $ZMAT DLC=.T. AUTO=.T.
>>>>>DLCTOL=1D-7 ORTTOL=1D-7 $end
>>>>> $INTGRL PACKAO=.true. $end
>>>>> $p2p p2p=.t. dlb=.t. $end
>>>>> $basis gbasis=TZV $end
>>>>> $PCM PCMTYP=DPCM SOLVNT=input RSOLV=2.155 EPS=35.688 EPSINF=1.806874 $END
>>>>> $PCMCAV RIN(58)=1.956 $END

>>>>>Typical out-file is attached.

>>>>>Thank you,


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