From owner-chemistry@ccl.net Fri Aug 1 07:55:01 2008 From: "Sue Lam chsue2004===yahoo.com" To: CCL Subject: CCL:G: Locating a broken-symmetry singlet state in Gaussian Message-Id: <-37474-080801074355-2531-O/wVR6CrGwGKKkil4cTyoQ],[server.ccl.net> X-Original-From: Sue Lam Content-Type: multipart/alternative; boundary="0-1888444919-1217587423=:31238" Date: Fri, 1 Aug 2008 03:43:43 -0700 (PDT) MIME-Version: 1.0 Sent to CCL by: Sue Lam [chsue2004]![yahoo.com] --0-1888444919-1217587423=:31238 Content-Type: text/plain; charset=iso-8859-1 Content-Transfer-Encoding: quoted-printable Dear Mariusz, =A0 Thank you for your reply. I am trying to locate a open-shell singlet=A0tran= sition state by using UDFT.=A0 What else that I need to check in order to c= onfirm that it is the=A0correct broken symmetry singlet state, other than t= he =A0correct occupation of singly alpha and beta orbitals and the=A0 non-z= ero vaule. =A0 Thanks a=A0 lot =A0 Sue --- On Thu, 7/31/08, Mariusz Radon mariusz.radon-,-gmail.com wrote: > From: Mariusz Radon mariusz.radon-,-gmail.com Subject: CCL:G: Locating a broken-symmetry singlet state in Gaussian To: "L, Sue " Date: Thursday, July 31, 2008, 5:16 PM Sent to CCL by: Mariusz Radon [mariusz.radon~~gmail.com] Sue L chsue2004:yahoo.com wrote: > Is it necessary to put a keyword guess=3Dmix, in order to locate a > broken-symmetry singlet state in Gaussian? If the molecule contains a > symmetry, in which the singly occupied alpha and beta orbitals are in > different symmetry, there is no need to put that keyword? >=20 Hi Sue, Is it enough or not, I think, it depends on particular case... You=20 always need to check whether you really have converged to a=20 broken-symmetry solution or not; AFAIK, even "guess=3Dmix" keyword doesn't=20 guarantee this. So, you need to inspect the molecular orbitals and/or=20 value after the calculations are finished. In such a case, that alpha and beta singly occupied orbitals belong to=20 different symmetries, a nice way to produce the broken symmetry solution=20 might be to manually permute the relevant orbitals (e.g. "guess=3Dalter")=20 and (probably) to use "scf=3Dsymm". best wishes, Mariusz Radon -=3D This is automatically added to each message by the mailing script =3D-http://www.ccl.net/cgi-bin/ccl/send_ccl_messageSubscribe/Unsubscribe:=20Job: http://www.ccl.net/jobs=20http://www.ccl.net/spammers.txt=0A=0A=0A --0-1888444919-1217587423=:31238 Content-Type: text/html; charset=us-ascii

Dear Mariusz,

 

Thank you for your reply. I am trying to locate a open-shell singlet transition state by using UDFT.  What else that I need to check in order to confirm that it is the correct broken symmetry singlet state, other than the  correct occupation of singly alpha and beta orbitals and the  non-zero <S**2> vaule.

 

Thanks a  lot

 

Sue

--- On Thu, 7/31/08, Mariusz Radon mariusz.radon-,-gmail.com <owner-chemistry-$-ccl.net> wrote:

From: Mariusz Radon mariusz.radon-,-gmail.com <owner-chemistry-$-ccl.net>
Subject: CCL:G: Locating a broken-symmetry singlet state in Gaussian
To: "L, Sue " <chsue2004-$-yahoo.com>
Date: Thursday, July 31, 2008, 5:16 PM

Sent to CCL by: Mariusz Radon [mariusz.radon~~gmail.com]
Sue L chsue2004:yahoo.com wrote:
> Is it necessary to put a keyword guess=mix, in order to locate a
> broken-symmetry singlet state in Gaussian? If the molecule contains a
> symmetry, in which the singly occupied alpha and beta orbitals are in
> different symmetry, there is no need to put that keyword?
> 

Hi Sue,

Is it enough or not, I think, it depends on particular case... You 
always need to check whether you really have converged to a 
broken-symmetry solution or not; AFAIK, even "guess=mix" keyword
doesn't 
guarantee this. So, you need to inspect the molecular orbitals and/or 
<S**2> value after the calculations are finished.

In such a case, that alpha and beta singly occupied orbitals belong to 
different symmetries, a nice way to produce the broken symmetry solution 
might be to manually permute the relevant orbitals (e.g.
"guess=alter") 
and (probably) to use "scf=symm".

best wishes,
Mariusz Radonhttp://www.ccl.net/cgi-bin/ccl/send_ccl_messagehttp://www.ccl.net/chemistry/sub_unsub.shtmlhttp://www.ccl.net/spammers.txt

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