From owner-chemistry |-at-| ccl.net Wed Feb  4 23:51:02 2009
From: "Sue Lam chsue2004#,#yahoo.com" <owner-chemistry**server.ccl.net>
To: CCL
Subject: CCL:G: Broken Symmetry Singlet Excited State
Message-Id: <-38555-090204224142-10972-7LRjA6x37X9Brs2cSjYLPg**server.ccl.net>
X-Original-From: Sue Lam <chsue2004|,|yahoo.com>
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Date: Wed, 4 Feb 2009 18:41:23 -0800 (PST)
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Sent to CCL by: Sue Lam [chsue2004**yahoo.com]
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Hello Chris,
=A0
Thank you very much for your reply. I am studying a reaction, in which the =
transition state=A0contain biradical character. I=A0have tired=A0to extract=
 the energy of the pure singlet from the broken symmetry state by using the=
 spin-correction procedure which was proposed by Yamaguchi et al (Chem. Phy=
s. Lett. 1994, 231, 25=9633)
=A0
E(singlet) =3D E(broken symmetry from UDFT) + fSC[E(broken symmetry from UD=
FT =96 E(triplet from UDFT))
=A0
Where fSC =3D 1<S^2> / [3<S^2> - 1<S^2>]
=A0
S^2: expectation value of the total spin
=A0
The S^2 before and after the annihilation are listed in the Gaussian output=
. In my case,=20
=A0
Annihilation of the first spin contaminant:
S^2 before annihilation=A0=A0=A0=A0 0.8631,=A0=A0 after=A0=A0=A0=A0 0.4136
=A0
I am not sure that whether I should use the S^2 before or after the annihil=
ation for the projection method.=20
=A0
Best regards,
Sue

--- On Wed, 2/4/09, Cristian V. Diaconu cvdiaconu!A!rice.edu <owner-chemist=
ry]|[ccl.net> wrote:

> From: Cristian V. Diaconu cvdiaconu!A!rice.edu <owner-chemistry]|[ccl.net>
Subject: CCL:G: Broken Symmetry Singlet Excited State
To: "L, Sue " <chsue2004]|[yahoo.com>
Date: Wednesday, February 4, 2009, 2:15 PM

Sent to CCL by: "Cristian V. Diaconu" [cvdiaconu~!~rice.edu]
Hello Sue,

The total energy reported by Gaussian is not for 'annihilated' wave
function, but for the single determinant that it uses in the Kohn-Sham sche=
me
(for DFT there isn't really any wave function).  There are ways to extract
the energy of the pure singlet from the broken symmetry state, but for DFT =
they
only work in certain cases.  Please look at discussions in:

J. Chem. Phys. 121, 10026 (2004)
J. Chem. Phys. 74, 5737 (1981)
Coord. Chem. Rev. 238=96239, 187 (2003)
C. J. Cramer, in Essentials of Computational Chemistry. Theories and Models=
.
(Wiley, Chichester, 2002), Chap. 14.4, pp. 456 =96 459.

For example, for a molecule with two unpaired electrons on two sites which
interact weakly (e.g., H2 molecule stretched, with a large bond length, say=
 10
Angstroms), if <S^2> ~ 1,

E(singlet) =3D 2 E(broken sym) - E(triplet)

I hope this helps.  If you have further questions, please include a little
detail on the system you are looking at.

Best regards,
Chris

Sue L chsue2004(~)yahoo.com wrote:
> Sent to CCL by: "Sue  L" [chsue2004..yahoo.com]
> Hi,=20
> I am running a DFT open-shell singlet calculation using Gaussian 03 to
obtain a broken symmetry singlet excited state. Does anyone know whether th=
e
electronic energy calculated at the end based on the annihilated wave funct=
ion
or not?=20
> Thank you very much!
>=20
> Best regards,
> Sue>=20
>=20
>=20

-- Cristian V. Diaconu
Postdoctoral Research Associate
Department of Chemistry - MS60
Rice University
PO Box 1892
Houston, TX 77251-1892
Phone: 713-348-3734
Email: cvdiaconu-x-rice.edu



-=3D This is automatically added to each message by the mailing script =3D-http://www.ccl.net/cgi-bin/ccl/send_ccl_messagehttp://www.ccl.net/chemistry/sub_unsub.shtmlhttp://www.ccl.net/spammers.txt=0A=0A=0A      
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<table cellspacing=3D"0" cellpadding=3D"0" border=3D"0" ><tr><td valign=3D"=
top" style=3D"font: inherit;"><P class=3DMsoNormal style=3D"MARGIN: 0cm 0cm=
 0pt"><FONT face=3D"Times New Roman" size=3D3>Hello Chris,</FONT></DIV>
<P class=3DMsoNormal style=3D"MARGIN: 0cm 0cm 0pt"><?xml:namespace prefix =
=3D o ns =3D "urn:schemas-microsoft-com:office:office" /><o:p><FONT face=3D=
"Times New Roman" size=3D3>&nbsp;</FONT></o:p></DIV>
<P class=3DMsoNormal style=3D"MARGIN: 0cm 0cm 0pt; mso-layout-grid-align: n=
one"><FONT size=3D3><FONT face=3D"Times New Roman">Thank you very much for =
your reply. I am studying a reaction, in which the transition state&nbsp;co=
ntain biradical character. I&nbsp;have tired&nbsp;to extract the energy of =
the pure singlet from the broken symmetry state by using the spin-correctio=
n procedure which was proposed by Yamaguchi et al (<I>Chem. Phys. Lett. </I=
><B>1994</B>, <I>231</I>, 25=9633)<I><o:p></o:p></I></FONT></FONT></DIV>
<P class=3DMsoNormal style=3D"MARGIN: 0cm 0cm 0pt; mso-layout-grid-align: n=
one"><o:p><FONT face=3D"Times New Roman" size=3D3>&nbsp;</FONT></o:p></DIV>
<P class=3DMsoNormal style=3D"MARGIN: 0cm 0cm 0pt; mso-layout-grid-align: n=
one"><FONT face=3D"Times New Roman" size=3D3>E(singlet) =3D E(broken symmet=
ry from UDFT) + fSC[E(broken symmetry from UDFT =96 E(triplet from UDFT))</=
FONT></DIV>
<P class=3DMsoNormal style=3D"MARGIN: 0cm 0cm 0pt; mso-layout-grid-align: n=
one"><o:p><FONT face=3D"Times New Roman" size=3D3>&nbsp;</FONT></o:p></DIV>
<P class=3DMsoNormal style=3D"MARGIN: 0cm 0cm 0pt; mso-layout-grid-align: n=
one"><FONT face=3D"Times New Roman" size=3D3>Where fSC =3D 1&lt;S^2&gt; / [=
3&lt;S^2&gt; - 1&lt;S^2&gt;]</FONT></DIV>
<P class=3DMsoNormal style=3D"MARGIN: 0cm 0cm 0pt; mso-layout-grid-align: n=
one"><o:p><FONT face=3D"Times New Roman" size=3D3>&nbsp;</FONT></o:p></DIV>
<P class=3DMsoNormal style=3D"MARGIN: 0cm 0cm 0pt; mso-layout-grid-align: n=
one"><FONT face=3D"Times New Roman" size=3D3>S^2: expectation value of the =
total spin</FONT></DIV>
<P class=3DMsoNormal style=3D"MARGIN: 0cm 0cm 0pt; mso-layout-grid-align: n=
one"><o:p><FONT face=3D"Times New Roman" size=3D3>&nbsp;</FONT></o:p></DIV>
<P class=3DMsoNormal style=3D"MARGIN: 0cm 0cm 0pt; mso-layout-grid-align: n=
one"><FONT face=3D"Times New Roman" size=3D3>The S^2 before and after the a=
nnihilation are listed in the Gaussian output. In my case, </FONT></DIV>
<P class=3DMsoNormal style=3D"MARGIN: 0cm 0cm 0pt; mso-layout-grid-align: n=
one"><FONT size=3D3><FONT face=3D"Times New Roman"></FONT></FONT>&nbsp;</DI=
V>
<P class=3DMsoNormal style=3D"MARGIN: 0cm 0cm 0pt; mso-layout-grid-align: n=
one"><FONT size=3D3><FONT face=3D"Times New Roman">Annihilation of the firs=
t spin contaminant:<o:p></o:p></FONT></FONT></DIV>
<P class=3DMsoNormal style=3D"MARGIN: 0cm 0cm 0pt; mso-layout-grid-align: n=
one"><FONT face=3D"Times New Roman" size=3D3>S^2 before annihilation<SPAN s=
tyle=3D"mso-spacerun: yes">&nbsp;&nbsp;&nbsp;&nbsp; </SPAN>0.8631,<SPAN sty=
le=3D"mso-spacerun: yes">&nbsp;&nbsp; </SPAN>after<SPAN style=3D"mso-spacer=
un: yes">&nbsp;&nbsp;&nbsp;&nbsp; </SPAN>0.4136</FONT></DIV>
<P class=3DMsoNormal style=3D"MARGIN: 0cm 0cm 0pt; mso-layout-grid-align: n=
one"><o:p><FONT face=3D"Times New Roman" size=3D3>&nbsp;</FONT></o:p></DIV>
<P class=3DMsoNormal style=3D"MARGIN: 0cm 0cm 0pt; mso-layout-grid-align: n=
one"><FONT face=3D"Times New Roman" size=3D3>I am not sure that whether I s=
hould use the S^2 before or after the annihilation for the projection metho=
d. </FONT></DIV>
<P class=3DMsoNormal style=3D"MARGIN: 0cm 0cm 0pt; mso-layout-grid-align: n=
one"><o:p><FONT face=3D"Times New Roman" size=3D3>&nbsp;</FONT></o:p></DIV>
<P class=3DMsoNormal style=3D"MARGIN: 0cm 0cm 0pt; mso-layout-grid-align: n=
one"><FONT face=3D"Times New Roman" size=3D3>Best regards,</FONT></DIV>
<P class=3DMsoNormal style=3D"MARGIN: 0cm 0cm 0pt; mso-layout-grid-align: n=
one"><FONT face=3D"Times New Roman" size=3D3>Sue</FONT></DIV><BR><BR>--- On=
 <B>Wed, 2/4/09, Cristian V. Diaconu cvdiaconu!A!rice.edu <I>&lt;owner-chem=
istry]|[ccl.net&gt;</I></B> wrote:<BR>
<BLOCKQUOTE style=3D"PADDING-LEFT: 5px; MARGIN-LEFT: 5px; BORDER-LEFT: rgb(=
16,16,255) 2px solid">From: Cristian V. Diaconu cvdiaconu!A!rice.edu &lt;ow=
ner-chemistry]|[ccl.net&gt;<BR>Subject: CCL:G: Broken Symmetry Singlet Excite=
d State<BR>To: "L, Sue " &lt;chsue2004]|[yahoo.com&gt;<BR>Date: Wedne=
sday, February 4, 2009, 2:15 PM<BR><BR><PRE>Sent to CCL by: "Cristian V. Di=
aconu" [cvdiaconu~!~rice.edu]
Hello Sue,

The total energy reported by Gaussian is not for 'annihilated' wave
function, but for the single determinant that it uses in the Kohn-Sham sche=
me
(for DFT there isn't really any wave function).  There are ways to extract
the energy of the pure singlet from the broken symmetry state, but for DFT =
they
only work in certain cases.  Please look at discussions in:

J. Chem. Phys. 121, 10026 (2004)
J. Chem. Phys. 74, 5737 (1981)
Coord. Chem. Rev. 238=96239, 187 (2003)
C. J. Cramer, in Essentials of Computational Chemistry. Theories and Models=
.
(Wiley, Chichester, 2002), Chap. 14.4, pp. 456 =96 459.

For example, for a molecule with two unpaired electrons on two sites which
interact weakly (e.g., H2 molecule stretched, with a large bond length, say=
 10
Angstroms), if &lt;S^2&gt; ~ 1,

E(singlet) =3D 2 E(broken sym) - E(triplet)

I hope this helps.  If you have further questions, please include a little
detail on the system you are looking at.

Best regards,
Chris

Sue L chsue2004(~)yahoo.com wrote:
&gt; Sent to CCL by: "Sue  L" [chsue2004..yahoo.com]
&gt; Hi,=20
&gt; I am running a DFT open-shell singlet calculation using Gaussian 03 to
obtain a broken symmetry singlet excited state. Does anyone know whether th=
e
electronic energy calculated at the end based on the annihilated wave funct=
ion
or not?=20
&gt; Thank you very much!
&gt;=20
&gt; Best regards,
&gt; Sue&gt;=20
&gt;=20
&gt;=20

-- Cristian V. Diaconu
Postdoctoral Research Associate
Department of Chemistry - MS60
Rice University
PO Box 1892
Houston, TX 77251-1892
Phone: 713-348-3734
Email: cvdiaconu-x-rice.edu



-=3D This is automatically added to each message by the mailing script =3D-http://www.ccl.net/cgi-bin/ccl/send_ccl_messagehttp://www.ccl.net/chemistry/sub_unsub.shtmlhttp://www.ccl.net/spammers.txt</PRE></BLOCKQUOTE></td></tr></table><br>=0A=0A      
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