From owner-chemistry@ccl.net Sun May 15 07:25:01 2016
From: "Robert Molt r.molt.chemical.physics_+_gmail.com" <owner-chemistry,server.ccl.net>
To: CCL
Subject: CCL: Not able to optimize structure - bisphosphole
Message-Id: <-52203-160515070454-9081-r3qUKURJQRlj1qccjdqLvA,server.ccl.net>
X-Original-From: Robert Molt <r.molt.chemical.physics-x-gmail.com>
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Date: Sun, 15 May 2016 12:04:44 +0100
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Sent to CCL by: Robert Molt [r.molt.chemical.physics^gmail.com]
I think using PM6 on a complicated wavefunction like tungsten is a bit 
ambitious. Tungsten can be a multi-reference wavefunction, and any 
single-determinant method (HF, DFT, PM6) may struggle.

First just focus on whether your choice in describing the wavefunction 
(PM6) can get the tungsten right. Put small ligands for the sake of 
testing. If you cannot get the small system with tungsten right, there 
is little point in the expensive calculation.

I would recommend starting with DFT as your lowest-order calculation to 
try to get a basic description of the system. But do you know the spins 
and multiplicities of the two metal atoms? DFT struggles with multiplets 
or high degeneracies, but is probably your best starting point.

On 5/15/16 3:28 AM, Suman Layek slayek|udcoled.com wrote:
> Sent to CCL by: Suman Layek [slayek.:.udcoled.com]
> Try nosymm
>
> ________________________________________
>> From: owner-chemistry+slayek==universaldisplay.com=ccl.net [owner-chemistry+slayek==universaldisplay.com=ccl.net] on behalf of Daniel Morales Salazar danielmoralessalazar91]_[gmail.com [owner-chemistry=ccl.net]
> Sent: Saturday, May 14, 2016 8:49 AM
> To: Suman Layek
> Subject: CCL: Not able to optimize structure - bisphosphole
>
> Sent to CCL by: "Daniel  Morales Salazar" [danielmoralessalazar91*|*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 using 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 calculation 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=           2 IAlg= 2 N=     3 NDim=     3 NE2=
> 2.
>   Diagonalization in DiagDN failed."
>
> MM methods crash with the message:
>
> " Error termination 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 Salazarhttp://www.ccl.net/cgi-bin/ccl/send_ccl_messagehttp://www.ccl.net/chemistry/sub_unsub.shtmlhttp://www.ccl.net/spammers.txt>
>