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Vyacheslav
kreme_vg@chemy.kolasc.net.ru

I've tried to run some calculations, being based on your hints (I have changed values of fshift and maxdii). It seems, calculations have gone (computers work three day)!
Thank you very much for help!

Best regards,
             Vyacheslav

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On Thu Aug 26 '10 11:18pm, Alexey A. Popov wrote
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>Dear Vyacheslav,

>there are different way how one can improve convergence, it is difficult to say without seeing your files.

>You can try fshift=XXX in $SCF group, by default the value is 0.1, you can try to increase it (or decrease it).

>You can also change the number of DIIS vectors by maxdii=XX command in $scf (default is 10, larger number can be sometimes better)

>If molecule is symmetric, symmetrization often helps

> $moorth symden=1 symvec=1 syms=1 $end
> $guess purify=1 symden=1 $end

>There are other ways you can play, check other threads on this forum

>Finally, 70 iterations is not a large number. I mean, in difficult situations you may need more to converge - at least, at the first step. If your starting geometry is not very bad, then at subsequent optimization steps the number of scf iterations needed is usually much smaller.
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