<= div id=3D"yiv3733130765yui_3_16_0_ym19_1_1463251158989_22609">Daniel--

<= div id=3D"yiv3733130765yui_3_16_0_ym19_1_1463251158989_22609">A few questio= ns, that may be useful to others even if not to me :-)

First regarding the MM method= s. The error message given is pretty generic. Does the calculat= ion produce any intermediate geometries, or does it crash on the first geom= etric-optimization step? If there are intermediate geometries,does th= e energy decrease from step to step, or is there a sudden increase in energ= y? Do you even have an atom type and parameters for tungsten? W= hich MM force field are you using?

[I would have advised opt=3Dcalcall a= s a last resort, but given the size of your molecule (which is surely even = bigger than the formula you actually wrote implies: how many carbon atoms a= gain? :-) I might have second thoughts on that. Hopefully someone has= a better idea.]

About the semiemprical method (PM6). &nb= sp;It appears from the error message that you are not getting a decent wave= function. Are you using guess=3Dread to get the wavefunction from the= checkpoint file in which you were able to optimize with opt=3Dloose? = ;(Or does guess=3Dread even work with semiempirical methods?) Are you= sure everything (especially the tungsten moieties) are in the correct elec= tronic state?

Hope this helps,

--David Shobe

On Saturday, May 14, 201= 6 9:10 AM, Daniel Morales Salazar danielmoralessalazar91]_[gmail.com <ow= ner-chemistry]-[ccl.net> wrote:

<= br clear=3D"none">Sent to CCL by: "Daniel Morales Salazar" [danielmor= alessalazar91*|*gmail.com]
Hello,

I am trying to optimize a molecule with the chemical formula= CH52O18P4S4W2, which contains thiophenes-phospholes, phenyl groups, and tungsten pentacarbonyl substituents.
It is a large and especially bulky molecule. I have tried u= sing MM and
Semi-empirical methods (PM6) unsuccessfully.= The only converged trial so
far was one with the "loose= " keyword using PM6, which crashed in the
following calc= ulation with stricter parameters when I did not use the
= keyword. I have tried the keywords calcfc, qc, cartesian, etc.

Any advice for these types of cases?

Semi-empirical jobs crash with the message:

"Symmetry turned off by external request. DSYEV returned Info=3D = 2 IAlg=3D 2 N=3D 3 NDim=3D 3 NE2=3D = ;
2.
Diagonaliz= ation in DiagDN failed."

MM methods cr= ash with the message:

" Error terminat= ion request processed by link 9999."

I= have the feeling that the initial geometries are not so bad even! Thank you very much for your help.

Sincerely,

Daniel Morales Sa= lazar

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