From chemistry-request@server.ccl.net Sun Apr 27 20:28:28 2003 Received: from ns.ciac.jl.cn ([202.98.16.1]) by server.ccl.net (8.11.6/8.11.0) with ESMTP id h3S0SIo19337 for ; Sun, 27 Apr 2003 20:28:24 -0400 Received: from zhang1 (localhost [127.0.0.1]) by ns.ciac.jl.cn (8.9.1/8.9.1) with SMTP id IAA25333; Mon, 28 Apr 2003 08:31:45 +0800 (CST) Message-Id: <200304280031.IAA25333@ns.ciac.jl.cn> From: "zjwu" To: "help@gaussian.com" CC: "chemistry@ccl.net" Subject: Re: Re: CCL:CPCM TS location X-mailer: Foxmail 4.2 [cn] Mime-Version: 1.0 Content-Type: multipart/alternative; boundary="=====002_Dragon120100783831_=====" Date: Fri, 2 May 2003 8:26:57 +0800 This is a multi-part message in MIME format. --=====002_Dragon120100783831_===== Content-Type: text/plain; charset="GB2312" Content-Transfer-Encoding: quoted-printable Dear Dr. Hess, Do you know any publications containing cpcm ts structure= calculations? I do find some papers on local minima= optimizations using cpcm, but did not see any paper on= transition state calculation using cpcm model? Any papers on this aspect are appreaciated. Best wishes, Zhijian Wu Dear Dr. Zhijian Wu, You have performed the steps I'd recommend, i.e. using the= gas-phase Hessian or the Hessian from an Onsager calculation. Since these= options did not work, it might be necessary to calculate the CPCM= Hessian. You cannot do this with "opt=3D(ts,calcfc)" in G98, but you can perform= a two-step job in which the first step uses "freq" and the second= job step uses "opt=3D(ts,rcfc)". You might also consider performing an = "opt=3Dqst3" calculation in which you use your Onsager model= optimized TS as the initial guess structure for the CPCM transition state. Regards, Jim Hess On Thursday, April 24, 2003, at 01:13 AM, zjwu wrote: >> Dear Dr. Hess, >> >> ?/DIV> >> >> I mean the job failing because the structure is not the TS= structure >> anymore. The calculation may converge but goes to different= geometry >> which I did not want. I have tried to read force constants at= cpcm >> calculation from either gas phase frequency calculation or= Onsager >> frequency calculation (these frequencies are obtained based= on the >> optimized geometry) (calculation using Onsager model works= well for >> the TS calculation).=A0In addition, I also tried= opt=3D(ts,calcfc), but as >> you know,=A0calcfc does not exist for=A0cpcm.=A0It seems g03 is= possible to >> calculate fc at cpcm level. >> >> ?/DIV> >> >> Hope I have made myself clear. >> >> ?/DIV> >> >> Thank you very much for your answer. >> >> ?/DIV> >> >> Best regards, >> >> ?/DIV> >> >> Zhijian Wu >> >> ?/DIV> >> >> >> << image.tiff> >> >> Dear=A0Dr.=A0Zhijian=A0Wu, >> = =A0=A0=A0=A0Is=A0this=A0job=A0failing=A0because=A0it=A0runs=A0out=A0of=A0optimization=A0cycl= es?=A0I'd >> ?/DIV> >> = need=A0to=A0know=A0more=A0details=A0about=A0what=A0is=A0going=A0wrong=A0before=A0I=A0mak= e?/DIV> >> = detailed=A0suggestions,=A0but=A0one=A0possible=A0way=A0to=A0improve=A0this=A0calcu= lation?/DIV> >> = is=A0to=A0calculate=A0the=A0force=A0constants=A0in=A0the=A0solution=A0phase,=A0then=A0= use?/DIV> >> = these=A0force=A0constants=A0to=A0start=A0the=A0transition=A0state=A0search..=A0Usu= ally=A0the >> ?/DIV> >> = gas-phase=A0Hessian=A0is=A0a=A0good=A0enough=A0approximation,=A0but=A0in=A0some=A0ca= ses?/DIV> >> = where=A0the=A0gas-phase=A0and=A0solution-phase=A0potential=A0energy=A0surfaces= =A0are?/DIV> >> = different=A0enough,=A0explicitly=A0calculating=A0the=A0second=A0derivatives=A0= in=A0the?/DIV> >> = solution=A0phase=A0can=A0be=A0helpful.=A0Incidentally,=A0if=A0you=A0are=A0using=A0G9= 8,=A0the?/DIV> >> = CPCM=A0second=A0derivatives=A0will=A0be=A0performed=A0by=A0numerical=A0different= iation?/DIV> >> = of=A0the=A0analytic=A0gradients=A0and=A0if=A0you=A0are=A0using=A0G03,=A0the=A0second?/= DIV> >> derivatives=A0will=A0be=A0calculated=A0analytically. >> ?/DIV> >> Regards, >> Jim=A0Hess >> ?/DIV> >> ++++++++++++++++++++++++++ >> James=A0Hess,=A0Ph.D. >> Customer=A0Support=A0Scientist >> Gaussian,=A0Inc. >> e-mail:=A0help@gaussian.com >> ++++++++++++++++++++++++++ >> ?/DIV> >> ?/DIV> >> On=A0Tuesday,=A0April?2,?003,=A0at?8:29=A0PM,=A0zjwu=A0wrote: >> ?/DIV> >> > > =A0Dear=A0members, >> > > >> > > ?/DIV> >> > > >> > > = =A0I=A0am=A0trying=A0to=A0locate=A0the=A0transition=A0state=A0using=A0cpcm=A0model.=A0Th= e?/DIV> >> > > = =A0initial=A0structure=A0is=A0from=A0gas=A0phase=A0optimized=A0transition=A0struct= ure?/DIV> >> > > >> = ?with=A0correct=A0vibrational=A0mode).=A0The=A0optimization=A0at=A0cpcm=A0level=A0= fails?/DIV> >> > > =A0by=A0the=A0following=A0keywords >> > > >> > > ?/DIV> >> > > >> > > >> = ?b3lyp/6-31g(d,p)=A0opt=3D(ts,=A0readfc,=A0noeigen)=A0scrf=3D(cpcm,solvent=3Dw= ater) >> > > >> > > ?/DIV> >> > > >> > > = =A0Do=A0anybody=A0has=A0experience=A0in=A0cpcm=A0transition=A0structure=A0calculat= ion? >> > > >> > > ?/DIV> >> > > >> > > =A0Thanks=A0a=A0lot. >> > > >> > > ?/DIV> >> > > >> > > =A0Best=A0regards, >> > > >> > > ?/DIV> >> > > >> > > =A0Zhijian=A0Wu >> > > Dear Dr. Zhijian Wu, You have performed the steps I'd recommend, i.e. using the gas-phase Hessian or the Hessian from an Onsager calculation.= Since these options did not work, it might be necessary to calculate= the CPCM Hessian. You cannot do this with "opt=3D(ts,calcfc)" in G98,= but you can perform a two-step job in which the first step uses= "freq" and the second job step uses "opt=3D(ts,rcfc)". You might also= consider performing an "opt=3Dqst3" calculation in which you use your= Onsager model optimized TS as the initial guess structure for the CPCM transition state. Regards, Jim Hess On Thursday, April 24, 2003, at 01:13 AM, zjwu wrote: << excerpt> Dear Dr. Hess, ?/DIV> I mean the job failing because the structure is not the TS= structure anymore. The calculation may converge but goes to different= geometry which I did not want. I have tried to read force constants at= cpcm calculation from either gas phase frequency calculation or= Onsager frequency calculation (these frequencies are obtained based on= the optimized geometry) (calculation using Onsager model works well= for the TS calculation).=A0In addition, I also tried opt=3D(ts,calcfc),= but as you know,=A0calcfc does not exist for=A0cpcm.=A0It seems g03 is= possible to calculate fc at cpcm level. ?/DIV> Hope I have made myself clear. ?/DIV> Thank you very much for your answer. ?/DIV> Best regards, ?/DIV> Zhijian Wu ?/DIV> << /excerpt> < < image.tiff> << excerpt> Dear=A0Dr.=A0Zhijian=A0Wu, =A0=A0=A0=A0Is=A0this=A0job=A0failing=A0because=A0it=A0runs=A0out=A0of=A0optimization=A0cycle= s?=A0I'd?/DIV> need=A0to=A0know=A0more=A0details=A0about=A0what=A0is=A0going=A0wrong=A0before=A0I=A0make= ?/DIV> detailed=A0suggestions,=A0but=A0one=A0possible=A0way=A0to=A0improve=A0this=A0calcul= ation?/DIV> is=A0to=A0calculate=A0the=A0force=A0constants=A0in=A0the=A0solution=A0phase,=A0then=A0u= se?/DIV> these=A0force=A0constants=A0to=A0start=A0the=A0transition=A0state=A0search..=A0Usua= lly=A0the?/DIV> gas-phase=A0Hessian=A0is=A0a=A0good=A0enough=A0approximation,=A0but=A0in=A0some=A0cas= es?/DIV> where=A0the=A0gas-phase=A0and=A0solution-phase=A0potential=A0energy=A0surfaces=A0= are?/DIV> different=A0enough,=A0explicitly=A0calculating=A0the=A0second=A0derivatives=A0i= n=A0the?/DIV> solution=A0phase=A0can=A0be=A0helpful.=A0Incidentally,=A0if=A0you=A0are=A0using=A0G98= ,=A0the?/DIV> CPCM=A0second=A0derivatives=A0will=A0be=A0performed=A0by=A0numerical=A0differenti= ation?/DIV> of=A0the=A0analytic=A0gradients=A0and=A0if=A0you=A0are=A0using=A0G03,=A0the=A0second?/D= IV> derivatives=A0will=A0be=A0calculated=A0analytically. ?/DIV> Regards, Jim=A0Hess ?/DIV> ++++++++++++++++++++++++++ James=A0Hess,=A0Ph.D. Customer=A0Support=A0Scientist Gaussian,=A0Inc. e-mail:=A0help@gaussian.com ++++++++++++++++++++++++++ ?/DIV> ?/DIV> On=A0Tuesday,=A0April?2,?003,=A0at?8:29=A0PM,=A0zjwu=A0wrote: ?/DIV> >> > =A0Dear=A0members, >> > >> > ?/DIV> >> > >> > = =A0I=A0am=A0trying=A0to=A0locate=A0the=A0transition=A0state=A0using=A0cpcm=A0model.=A0Th= e?/DIV> >> > = =A0initial=A0structure=A0is=A0from=A0gas=A0phase=A0optimized=A0transition=A0struct= ure?/DIV> >> > ?with=A0correct=A0vibrational=A0mode).=A0The=A0optimization=A0at=A0cpcm=A0level=A0f= ails?/DIV> >> > =A0by=A0the=A0following=A0keywords >> > >> > ?/DIV> >> > >> > ?b3lyp/6-31g(d,p)=A0opt=3D(ts,=A0readfc,=A0noeigen)=A0scrf=3D(cpcm,solvent=3Dwa= ter) >> > >> > ?/DIV> >> > >> > = =A0Do=A0anybody=A0has=A0experience=A0in=A0cpcm=A0transition=A0structure=A0calculat= ion? >> > >> > ?/DIV> >> > >> > =A0Thanks=A0a=A0lot. >> > >> > ?/DIV> >> > >> > =A0Best=A0regards, >> > >> > ?/DIV> >> > >> > =A0Zhijian=A0Wu >> > << /excerpt> --=====002_Dragon120100783831_===== Content-Type: text/html; charset="GB2312" Content-Transfer-Encoding: quoted-printable

Dear Dr. Hess,

 

Do you know any publications containing cpcm ts structure= calculations? I do find some papers on local minima optimizations using cpcm,= but did not see any paper on transition state calculation using cpcm model?

 

Any papers on this aspect are appreaciated.

 

Best wishes,

 

Zhijian Wu

Dear Dr. Zhijian Wu,
    You have performed th= e steps I'd recommend, i.e. using t= he gas-phase  
Hessian or the Hessian from an = ;Onsager calculation. Since these options&nbs= p; 
did not work, it might be nece= ssary to calculate the CPCM Hessian.&nbs= p;You  
cannot do this with "opt=3D(ts,calcfc)"&nb= sp;in G98, but you can perform a&nb= sp; 
two-step job in which the first&nbs= p;step uses "freq" and the second j= ob  
step uses "opt=3D(ts,rcfc)". You might&nbs= p;also consider performing an  
"opt=3Dqst3" calculation in which you = ;use your Onsager model optimized TS&nbs= p; 
as the initial guess structure for&= nbsp;the CPCM transition state.
 
Regards,
Jim Hess
 
On Thursday, April 24, 2003, at&nbs= p;01:13 AM, zjwu wrote:
 
>>  Dear Dr. Hess,
>>
>>  ?/DIV>
>>
>>  I mean the job failing because&nbs= p;the structure is not the TS struc= ture  
>>  anymore. The calculation may converge&n= bsp;but goes to different geometry  = ;
>>  which I did not want. I have&= nbsp;tried to read force constants at&nb= sp;cpcm  
>>  calculation from either gas phase = frequency calculation or Onsager  
=
>>  frequency calculation (these frequencies&nbs= p;are obtained based on the  
=
>>  optimized geometry) (calculation using = Onsager model works well for  
>>  the TS calculation).=A0In addition, I&nbs= p;also tried opt=3D(ts,calcfc), but as &nb= sp;
>>  you know,=A0calcfc does not exist fo= r=A0cpcm.=A0It seems g03 is possible to = ; 
>>=  calculate fc at cpcm level.
>>
>>  ?/DIV>
>>
>>  Hope I have made myself clear.
>>
>>  ?/DIV>
>>
>>  Thank you very much for your = answer.
>>
>>  ?/DIV>
>>
>>  Best regards,
>>
>>  ?/DIV>
>>
>>  Zhijian Wu
>>
>>  ?/DIV>
>>
>>
>>
<< image.tiff>
>>
>>  Dear=A0Dr.=A0Zhijian=A0Wu,
>>  =A0=A0=A0=A0Is=A0this=A0job=A0failing=A0because=A0it=A0runs=A0out=A0of=A0optimization= =A0cycles?=A0I'd 
>>  ?/DIV>
>>  need=A0to=A0know=A0more=A0details=A0about=A0what=A0is=A0going=A0wrong=A0before=A0= I=A0make?/DIV>
>>  detailed=A0suggestions,=A0but=A0one=A0possible=A0way=A0to=A0improve=A0this=A0= calculation?/DIV>
>>  is=A0to=A0calculate=A0the=A0force=A0constants=A0in=A0the=A0solution=A0phase,=A0= then=A0use?/DIV>
>>  these=A0force=A0constants=A0to=A0start=A0the=A0transition=A0state=A0search.= .=A0Usually=A0the 
>>  ?/DIV>
>>  gas-phase=A0Hessian=A0is=A0a=A0good=A0enough=A0approximation,=A0but=A0in=A0so= me=A0cases?/DIV>
>>  where=A0the=A0gas-phase=A0and=A0solution-phase=A0potential=A0energy=A0sur= faces=A0are?/DIV>
>>  different=A0enough,=A0explicitly=A0calculating=A0the=A0second=A0derivat= ives=A0in=A0the?/DIV>
>>  solution=A0phase=A0can=A0be=A0helpful.=A0Incidentally,=A0if=A0you=A0are=A0usi= ng=A0G98,=A0the?/DIV>
>>  CPCM=A0second=A0derivatives=A0will=A0be=A0performed=A0by=A0numerical=A0diff= erentiation?/DIV>
>>=  of=A0the=A0analytic=A0gradients=A0and=A0if=A0you=A0are=A0using=A0G03,=A0the=A0se= cond?/DIV>
>>=  derivatives=A0will=A0be=A0calculated=A0analytically.
>>  ?/DIV>
>>  Regards,
>>  Jim=A0Hess
>>  ?/DIV>
>>  ++++++++++++++++++++++++++
>>  James=A0Hess,=A0Ph.D.
>>  Customer=A0Support=A0Scientist
>>  Gaussian,=A0Inc.
>>  e-mail:=A0help@gaussian.com
>>  ++++++++++++++++++++++++++
>>  ?/DIV>
>>  ?/DIV>
>>=  On=A0Tuesday,=A0April?2,?003,=A0at?8:29=A0PM,=A0zjwu=A0wrote:
>>  ?/DIV>
>>  > >  =A0Dear=A0members,
>>  > >
>>  > >  ?/DIV>
>>  > >
>>  > >  =A0I=A0am=A0trying=A0to=A0locate=A0the=A0transition=A0state=A0using=A0cpcm=A0mode= l.=A0The?/DIV>
>>  > >  =A0initial=A0structure=A0is=A0from=A0gas=A0phase=A0optimized=A0transition=A0s= tructure?/DIV>
>>  > >   
>>  ?with=A0correct=A0vibrational=A0mode).=A0The=A0optimization=A0at=A0cpcm=A0l= evel=A0fails?/DIV>
>>  > >=  =A0by=A0the=A0following=A0keywords
>>  > >
>>  > >  ?/DIV>
>>  > >
>>  > >   
>>  ?b3lyp/6-31g(d,p)=A0opt=3D(ts,=A0readfc,=A0noeigen)=A0scrf=3D(cpcm,solv= ent=3Dwater)
>>  > >
>>  > >  ?/DIV>
>>  > >
>>  > >  =A0Do=A0anybody=A0has=A0experience=A0in=A0cpcm=A0transition=A0structure=A0cal= culation?
>>  > >
>>  > >  ?/DIV>
>>  > >
>>  > >  =A0Thanks=A0a=A0lot.
>>  > >
>>  > >  ?/DIV>
>>  > >
>>  > >  =A0Best=A0regards,
>>  > >
>>  > >  ?/DIV>
>>  > >
>>  > >  =A0Zhijian=A0Wu
>>  > >
Dear Dr. Zhijian Wu,
 
   You have performed the = ;steps I'd recommend, i.e. using the
gas-phase Hessian or the Hessian fr= om an Onsager calculation. Since
these options did not work, it = ;might be necessary to calculate the
CPCM Hessian. You cannot do this&nb= sp;with "opt=3D(ts,calcfc)" in G98, but
you can perform a two-step job = ;in which the first step uses "freq= " and
the second job step uses "opt=3D(ts,r= cfc)". You might also consider
performing an "opt=3Dqst3" calculation in&= nbsp;which you use your Onsager
model optimized TS as the initial&n= bsp;guess structure for the CPCM
transition state. 
 
 
Regards,
 
Jim Hess
 
 
On Thursday, April 24, 2003, at&nbs= p;01:13 AM, zjwu wrote:
 
 
<< excerpt> Dear Dr. Hess,
 
 
?/DIV>
 
 
I mean the job failing because = ;the structure is not the TS struct= ure
anymore. The calculation may converge&nb= sp;but goes to different geometry
which I did not want. I have&n= bsp;tried to read force constants at&nbs= p;cpcm
calculation from either gas phase f= requency calculation or Onsager
frequency calculation (these frequencies = ;are obtained based on the
optimized geometry) (calculation using O= nsager model works well for
the TS calculation).=A0In addition, I = ;also tried opt=3D(ts,calcfc), but as
you know,=A0calcfc does not exist for= =A0cpcm.=A0It seems g03 is possible to
=
calculate fc at cpcm level.
 
 
?/DIV>
 
 
Hope I have made myself clear.
 
 
?/DIV>
 
 
Thank you very much for your a= nswer.
 
 
?/DIV>
 
 
Best regards,
 
 
?/DIV>
 
 
Zhijian Wu
 
 
?/DIV>
 
 
 
 
<< /excerpt> < < image.tiff>
 
<< excerpt>
 
Dear=A0Dr.=A0Zhijian=A0Wu,
 
=A0=A0=A0=A0Is=A0this=A0job=A0failing=A0because=A0it=A0runs=A0out=A0of=A0optimization=A0= cycles?=A0I'd?/DIV>
 
need=A0to=A0know=A0more=A0details=A0about=A0what=A0is=A0going=A0wrong=A0before=A0I= =A0make?/DIV>
 
detailed=A0suggestions,=A0but=A0one=A0possible=A0way=A0to=A0improve=A0this=A0c= alculation?/DIV>
 
is=A0to=A0calculate=A0the=A0force=A0constants=A0in=A0the=A0solution=A0phase,=A0t= hen=A0use?/DIV>
 
these=A0force=A0constants=A0to=A0start=A0the=A0transition=A0state=A0search..= =A0Usually=A0the?/DIV>
 
gas-phase=A0Hessian=A0is=A0a=A0good=A0enough=A0approximation,=A0but=A0in=A0som= e=A0cases?/DIV>
 
where=A0the=A0gas-phase=A0and=A0solution-phase=A0potential=A0energy=A0surf= aces=A0are?/DIV>
 
different=A0enough,=A0explicitly=A0calculating=A0the=A0second=A0derivati= ves=A0in=A0the?/DIV>
 
solution=A0phase=A0can=A0be=A0helpful.=A0Incidentally,=A0if=A0you=A0are=A0usin= g=A0G98,=A0the?/DIV>
 
CPCM=A0second=A0derivatives=A0will=A0be=A0performed=A0by=A0numerical=A0diffe= rentiation?/DIV>
 
of=A0the=A0analytic=A0gradients=A0and=A0if=A0you=A0are=A0using=A0G03,=A0the=A0seco= nd?/DIV>
 
derivatives=A0will=A0be=A0calculated=A0analytically.
 
?/DIV>
 
Regards,
 
Jim=A0Hess
 
?/DIV>
 
++++++++++++++++++++++++++
 
James=A0Hess,=A0Ph.D.
 
Customer=A0Support=A0Scientist
 
Gaussian,=A0Inc.
 
e-mail:=A0help@gaussian.com
 
++++++++++++++++++++++++++
 
?/DIV>
 
?/DIV>
 
On=A0Tuesday,=A0April?2,?003,=A0at?8:29=A0PM,=A0zjwu=A0wrote:
 
?/DIV>
 
>> >  =A0Dear=A0members,
 
>> >
 
>> >  ?/DIV>
 
>> >
 
>> >  =A0I=A0am=A0trying=A0to=A0locate=A0the=A0transition=A0state=A0using=A0cpcm=A0mode= l.=A0The?/DIV>
 
>> >  =A0initial=A0structure=A0is=A0from=A0gas=A0phase=A0optimized=A0transition=A0s= tructure?/DIV>
 
>> >
?with=A0correct=A0vibrational=A0mode).=A0The=A0optimization=A0at=A0cpcm=A0le= vel=A0fails?/DIV>
 
>> >  =A0by=A0the=A0following=A0keywords
 
>> >
 
>> >  ?/DIV>
 
>> >
 
>> >
?b3lyp/6-31g(d,p)=A0opt=3D(ts,=A0readfc,=A0noeigen)=A0scrf=3D(cpcm,solve= nt=3Dwater)
 
>> >
 
>> >  ?/DIV>
 
>> >
 
>> >  =A0Do=A0anybody=A0has=A0experience=A0in=A0cpcm=A0transition=A0structure=A0cal= culation?
 
>> >
 
>> >  ?/DIV>
 
>> >
 
>> >  =A0Thanks=A0a=A0lot.
 
>> >
 
>> >  ?/DIV>
 
>> >
 
>> >  =A0Best=A0regards,
 
>> >
 
>> >  ?/DIV>
 
>> >
 
>> >  =A0Zhijian=A0Wu
 
>> >
 
<< /excerpt>
--=====002_Dragon120100783831_=====-- From chemistry-request@server.ccl.net Sun Apr 27 19:15:49 2003 Received: from mail.hubwest.com ([65.164.117.120]) by server.ccl.net (8.11.6/8.11.0) with ESMTP id h3RNFno12521 for ; Sun, 27 Apr 2003 19:15:49 -0400 Received: from hojicha [66.55.23.159] by mail.hubwest.com with ESMTP (SMTPD32-7.07) id A715311100F0; Sun, 27 Apr 2003 17:26:13 -0600 Content-Type: text/plain; charset="us-ascii" From: Matt Challacombe Reply-To: MChalla@LANL.Gov Organization: Group T-12, Los Alamos National Lab To: CHEMISTRY@ccl.net Subject: xyz->zmat->xyz Date: Sun, 27 Apr 2003 17:07:14 -0600 User-Agent: KMail/1.4.3 MIME-Version: 1.0 Message-Id: <200304271707.14141.MChalla@LANL.Gov> X-Note: This E-mail was scanned by declude Hubwest Internet (www.hubwest.com) for spam. Content-Transfer-Encoding: 8bit X-MIME-Autoconverted: from quoted-printable to 8bit by server.ccl.net id h3RNFno12522 Hi, Is there a simple program for converting from xyz to z-matrix and back? I've spent quite a while examining different versions of babel, but none of them seem to work in this capacity... Thx, Matt -- Matt Challacombe Theoretical Division, Los Alamos http://www.t12.lanl.gov/~mchalla/ From chemistry-request@server.ccl.net Sun Apr 27 07:53:41 2003 Received: from compchem.dfh.dk ([130.225.225.51]) by server.ccl.net (8.11.6/8.11.0) with ESMTP id h3RBreo02611 for ; Sun, 27 Apr 2003 07:53:40 -0400 Received: from compchem.dfh.dk (localhost [127.0.0.1]) by compchem.dfh.dk (SGI-8.12.5/8.12.5) with ESMTP id h3RBrlrr312922 for ; Sun, 27 Apr 2003 13:53:47 +0200 (MEST) Received: (from jeremy@localhost) by compchem.dfh.dk (SGI-8.12.5/8.12.5/Submit) id h3RBrkbG313546 for CHEMISTRY@ccl.net; Sun, 27 Apr 2003 13:53:46 +0200 (MEST) Date: Sun, 27 Apr 2003 13:53:46 +0200 From: "Jeremy R. Greenwood" To: CHEMISTRY@ccl.net Subject: Ab initio prediction of time-averaged NMR shifts Message-ID: <20030427135346.A312410@compchem.dfh.dk> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii X-Mailer: Mutt 1.0i Dear CCL, Question: can someone provide a reference/suggestion/theory/method/example for extending ab initio NMR chemical shift prediction to the reproduction of time-averaged shifts for systems in rapid equilibrium? -- My problem: I have characterised a potential energy surface (to basis set convergence with B3LYP) of a strained system as [1] -- TS1,2 -- [2] -- TS2,3 -- [3] Where the transitions involve (et al.) ca. 60 degree torsional sweeps about RCH2--N-oxide(RR')--CH2R bonds. The barriers are modest, and at normal temperatures the interchange is rapid, thus the NMR spectrum gives a sharp-line average. I have calculated magnetic shielding tensors for minima and transition states, and could in principle do it for points along the path. The 1H proton shifts vary dramatically over the energy surface as the protons move in the shadow of the chiral N-O. I doubt a naive approach of linearly combining the shifts of the minima according to relative energy will tell the story of the time-averaged structure and its magnetic properties. Thanks in advance for any suggestions. Jeremy ---------------------------------------------------------------------- Jeremy Greenwood jeremy@greenwood.net Department of Medicinal Chemistry bh +45 35306117 The Danish University of Pharmaceutical Sciences fx +45 35306040 Universitetsparken 2, DK-2100 Copenhagen, Denmark ah +45 32598030 ----------------------------------------------------------------------