# CCL:G: ri-dft (bp86/def-SVP) calculations for Mn(V) oxo porphyrin dimer

*From*: Uwe Huniar <uwe.huniar- -cosmologic.de>
*Subject*: CCL:G: ri-dft (bp86/def-SVP) calculations for Mn(V) oxo
porphyrin dimer
*Date*: Tue, 26 Jun 2007 14:46:28 +0200

Sent to CCL by: Uwe Huniar [uwe.huniar . cosmologic.de]
Hello,
the SCF convergence in Turbomole can be controlled by:
1. the maximum number of SCF iterations ($scfiterlimit)
2. using a higher DIIS damping ($scfdamp), I would recommend to start with a
damping factor between 4 to 8. If that does not help, try:
2.a) set the damping factor to a high value like 15, and limit the number of
SCF iterations to, say, 20.
2.b) after that, reduce the damping factor to something like 4 and continue
with $scfiterlimit of 300 (or so).
You can check the convergence graphically (if gnuplot is installed) by calling
cgnce <output-filename>
and if the energy starts to oscillate, the damping factor is too high...
3. using another orbital shift ($scforbitalshift)
All other procedures might alter your occupation, and that is something you do
not want to have in your case.
There is a short chapter (6.9) about SCF convergence also in the Tutorial of
TURBOMOLE, which can be found in the DOC directory of your Turbomole
installation. A detailed description of the keywords can be found in the
documentation.
Yours,
Uwe
> I am doing some ri-dft (bp86/def-SVP) calculations for Mn(V) oxo porphyrin
> dimer system(s) with TURBOMOLE 5.9.0
>
> I managed to optimize the ferromagnatically (F) coupled nonet spin state (F
> copled quintets of the individual Mn sites) for the above system. Then I
> tried to optimize the anti-ferromagnatically coupled singlet (AF copled
> quintets of the individual Mn sites) using the orbitals, geometry of the F
> coupled nonet and assigning the exact electron occupancy. But SCF
convergence
> for the AF singlet was not succeeded. After that, I followed the same
> procedure with dft (b3-lyp/def-SVP), but it did not work.
>
> According to my previous calculations with GAUSSIAN 03 for the same
> system(s), AF coupled electronic configurations are quite important than F
> coupled spin states. But G03 calculations are time consuming. If I would
> manage to optimize the AF coupled spin states using ri-dft, I can save my
> time.
>
> Any comments would be appreciated.
>
>
> W. M. C. Sameera (PhD student)