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Alex Granovsky
gran@classic.chem.msu.su

Actually, the better approach that is also working (I've checked with RM1) is to set:

 $zmat cnvtol=1d-7 $end

The default is cnvtol=1d-8. This parameter defines the
acceptable tolerance for conversion internals to cartesians.


>>>Additional question:
>>>If the constrained optimization is successful, is there a way to relax the constrained optimized geometry in small steps, to increase the chances that the constraint does not vanish?

Yes it is possible... fortunately this is well documented
in the manual - look at TRMAX/DXMAX variables of $statpt
and use them to limit maximum geometry optimization step.

E.g. $statpt dxmax=0.05 trmax=0.05 $end

Regards,
Alex


On Wed Dec 2 '09 7:26pm, Richard wrote
--------------------------------------
>Actually, itbmat doesn't help here. Something that does work, at least for the HF/MINI or AM1 versions of the input provided, is adding tortol=170 to the $ZMAT group, a tip Alex gave me some time ago (don't think its documented ?).

>Richard

>On Wed Dec 2 '09 3:45pm, Dominic P. Guaņa wrote
>-----------------------------------------------
>>Try increasing ITBMAT=50 or ITBMAT=200 in the $STATPT Group, this will increase the number of iterations from internals to catersians.

>>On Tue Dec 1 '09 9:04pm, Valentin Monev wrote
>>---------------------------------------------
>>>Dear Alex,

>>>In a geometry optimization with nzvar=1 d5=1 and dlc=1 auto=1,
>>>I would like to freeze the distance between atoms 14 and 23, so I use
>>>ifrzat(1)=14,23. I get (see attached input and output files)

>>>THE CONVERSION FROM INTERNALS TO CARTESIANS
>>>DID NOT CONVERGE IN   10 ITERATIONS.
>>>MAX PRIMITIVE INTERNAL COORDINATE DEVIATION IS   0.00000003
>>>INTERNAL COORDINATES SELF-INCONSISTENCY     IS ************

>>>Is there a way to carry out this geometry optimization using the chosen (spherical)
>>>cc-pvtz (aug on N, O, etc.) basis set, together with dlc?

>>>Additional question:
>>>If the constrained optimization is successful, is there a way to relax the constrained optimized geometry in small steps, to increase the chances that the constraint does not vanish?

>>>Many thanks in advance,

>>>Valentin