Subject: Tansition states....summary

From: michael nolan <[email-masked]>
Date: Sat, 15 Mar 1997 17:00:32 +0000 (GMT)

Hi CCL...

Thanks to the replies for my (amended) query on transition states...

the answers are summarised below

michael

	The imp himself has spoken

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Michael Nolan (nearly BSc.)			Dublin City University (quantum chem.)
41 Woodview					Chemistry + german Year 4
Lucan
Co. Dublin
Ireland / Republic of Ireland / ROI / Eire

Email: [email-masked]

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Original question:

>hello CCL

>It seems that my question on trnasition states and PES was too vague...

>What I want to know is the following:
>I am reading a paper from Merrill, Gronert and Kass J. Phys. Chem. A
>1997, 101, 208-218.
>In this paper they use DFT to study the PES of a base induced elimination.
>My question is what would be the input for such a calculation {on
>Gaussian92/DFT}? Is the input the same for an ab initio calculation?

>michael

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Answer 1:

From [email-masked] Mar 14 08:58:31 1997
Date: Wed, 5 Mar 1997 07:55:34 -0600 (CST)
From: Richard Walsh <[email-masked]>
To: [email-masked]
Subject: Re: CCL:G:Transition states...

Michael,

One set of Gaussian 94 keywords that would perform a DFT transition
search would be:

%mem=8000000
%chk=dft_tstate.chk
#p b3lyp/cc-pVDZ opt=(ef,ts,z-matrix) scf=direct

This assumes that you have a starting geometry which has a PES
with the right curvature and your input file is in z-matrix format.
The calculation is performed by recomputing the integrals; the
eigenvector following algorithm for the PES surface search is
used. Memory requested is 8M words. Checkpoint data goes to the
file dft_tstate.chk. the '#p' forces printing of link related
entry and exit information.

Richard Walsh
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answer 2:

>From [email-masked] Fri Mar 14 08:58:51 1997
Date: Wed, 5 Mar 1997 12:26:54 -0600 (CST)
From: Steven Kass <[email-masked]>
To: [email-masked]
Subject: CCL:G:Transition states... (fwd)

 Michael,

 With regard to your question below, the simple answer is yes! To run a
 DFT calculation with G92/DFT one simply specifies the method (BVWN, BLYP,
 B3LYP, etc.), a basis set (6-31+G(d,p), aug-cc-pVDZ, etc.), and of
 course a starting geometry (in the case of the base induced
 eliminations some of these are transition states so one will need to
 specify opt=ts instead of just opt, but this is equally true for ab
 initio methods).

 Hope this helps.

 Steven

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Answer 3:
>From [email-masked] Wed Mar  5 05:33 EST 1997
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Date: Wed, 05 Mar 1997 11:25:04 +0100
From: [email-masked] (Marc Le Bret)
Subject: Re:  CCL:G:Transition states...

yes, just substitute MP2 by B3LYP for instance.
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* Marc LE BRET  *Laboratoire de Physicochimie et de Pharmacologie*
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Answer 4:

From [email-masked] Mar 14 08:59:26 1997
Date: Fri, 7 Mar 1997 09:51:48 -0500 (EST)
From: Doug Fox <[email-masked]>
To: Mick the imp <[email-masked]>
Subject: Re: CCL:G:Transition states...

  Michael,

    With G92/DFT the input for finding transition states(TS) starts with an
input structure which approximates the TS and then use OPT=TS or in most
cases OPT=(CALCFC,TS) to optimize the structure forcing a maximum in one
direction.  The only difference between DFT and ab initio methods for this
would be the keyword selecting the method, i.e. HF vs BLYP.

 Douglas J. Fox
  Director of Technical Support
  [email-masked]

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