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Re^2: Problem with SCF after couple steps of geometry optimization

Solntsev Pasha
solntsev@univ.kiev.ua


Dear Alex.

Thank you for the comments. A group-theoretical analysis for ferrocene predicts that HOMO should be a single degenerated orbital (D5h). While HOMO-1 and HOMO-2 are double degenerated. Such order absolutely in agreement with all experimental data. I would assume that for cation the symmetry should be preserved. It has also been shown that HF and DFT flip the single degenerated and the double degenerated orbitals. Thus, within HF and DFT HOMO consists of two double degenerated orbitals. I already started to optimize a geometry of the cation and the mentioned orbitals are in a correct order.

I totally agree that MCSCF may be the best choice for methalocences. However, for me ferrocenium cation is a reference for much bigger system and unfortunately i will  not be able to use the MCSCF approach for them.

Since i already have convergence, i will play a little and hopefully will get what i want.

Sincerely.
Pavel.






On Tue Apr 2 '13 3:15am, Alex Granovsky wrote
---------------------------------------------
>Dear Pavel,

>I would expect difficulties with this molecule.
>Do you know what is its expected molecular symmetry?
>The electronic state? Where the positive charge is located?

>It may be well the case that you need MCSCF for ferrocene cation.

>All the best,
>Alex
>
>
>
>
>On Mon Apr 1 '13 6:11am, Solntsev Pasha wrote
>---------------------------------------------
>>Dear friends.

>>I have a problem. I am trying to optimize geometry of ferrocene^(+1) molecule. I use cc-pVDZ basis set for all my calculations. Initially, i optimized geometry of ferrocene+hessian and then used equilibrium geometry to optimize the geometry of ferrocinium cation using UHF wave function MULT=2 icharg=1. I also used $statpt ststep=0.15  $end.

>>Then i started new calculation with DFT level of theory BPW91 functional I used converged geometry and MO vectors from the HF job to start the DFT job. I was able to converge the first SCF only with SOSCF=.t. ,  DIIS=.t. didn't work. So, using soscf=.t. i started geometry optimization. However, after two steps of geometry optimization the SCF can't be converged. So far, i used default GDIIS method. But i am not sure what parameters i can use to tune gdiis algorithm.

>>I used C1 symmetry for all my calculations. I also wasn't sure do we need to use d5=.t. for the spherical basis set and C1 point group?

>>Relevant part of the input file presented below. Any advice?

>> $CONTRL MAXIT=300 NZVAR=1
>> inttyp=hondo icut=11 itol=30
>> exetyp=run d5=.t. dfttyp=bpw91
>> runtyp=optimize scftyp=uhf  
>> icharg=1 mult=2 $END
>> $SYSTEM TIMLIM=2736 mwords=20  $END
>> $zmat auto=.t. dlc=.t. $end
>> $SCF FDIFF=.FALSE. dirscf=.t. soscf=.t. diis=.f. nconv=7
>> rstrct=.t.  $END
>> $guess guess=moread norb=249 $end
>> $basis gbasis=cc-pVDZ extfil=.t.  $end
>> $statpt opttol=1d-6 nstep=200 hssend=.t. ststep=0.1 $end
>> $DATA

>>Pavel.
>>


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