Subject: Re: No Subject Given By The Author

From: Shotgun <[email-masked]>
Date: Wed, 20 Sep 2000 14:54:22 +0200

I am a student of Faculty of Natural Sciences of UPJS and I am trying to
compute ( using programme GAMESS ) the general reaction path of addition of
ammonia to NCS group.

But there is a problem with one IRC calculation.
I have found a transition state,hessian computed at this transition geometry
has one and only one imaginatory frequency ( value about 2060 ), so ti seems
to be OK.I have also tried different methods of finding TS and all resulted
to the same structure and same value of imaginatory frequency.But an IRC
calculation stops after computing the first point,because the energy of
this point is higher than the energy of TS.

Please send me some advices,how to solve this problem.My address is
[email-masked]
Thank you.

---

From: "Phillip Matz" <[email-masked]>
Date: Wed, 20 Sep 2000 10:00:19 -0700

Hello!

It sounds like the IRC is following a reaction path which is leading to a
saddle point instead of a the standard "reactants go to products" IRC you
would like to see with your TS.  Just a thought...

If the above is true then your options/problems have increased tenfold - you
can try to characterize the system better by searching for a 2nd order
saddle point (an option for the OPT keyword), or you can try and force the
IRC to follow the reaction coordinate which would give you a standard
reaction path.  To do this try the PHASE switch for the IRC keyword.

Hope that helps a little!

Respectfully,
Phillip Matz

[email-masked]

----- Original Message -----
From: "Shotgun" <[email-masked]>
To: <[email-masked]>
Sent: Wednesday, September 20, 2000 5:54 AM
Subject: No Subject Given By The Author

> -= This is automatically added to each message by mailing script =-
> [email-masked] -- To Everybody    |   [email-masked] -- To
Admins
> [email-masked] -- HELP CHEMISTRY or HELP SEARCH
> [email-masked] -- archive search    |    Gopher: gopher.ccl.net
70
> Ftp: ftp.ccl.net  |  WWW: http://www.ccl.net/chemistry/   | Jan:
[email-masked]

---

From: Jordi Villa <[email-masked]>
Date: Wed, 20 Sep 2000 11:02:38 -0700

I would use a smaller stepsize. Probably the first step in your calculation is so
large that you are not in the "valley" anymore.

> [email-masked] -- To Everybody    |   [email-masked] -- To Admins
> [email-masked] -- archive search    |    Gopher: gopher.ccl.net 70
> Ftp: ftp.ccl.net  |  WWW: http://www.ccl.net/chemistry/   | Jan: [email-masked]

--
Jordi Villa i Freixa
[email-masked]   http://laetro.usc.edu/wgroup/people/jorgevil
Department of Chemistry, University of Southern California
Los Angeles, CA, USA, 90089-1062
Tlf: 1-(213)-740 7671 Fax: 1-(213)-740 2701