Subject: RE: nth-order saddle point, n>1

From: "Robinson, James" <[email-masked]>
Date: Thu, 7 Jun 2001 09:13:56 +0100

A transition state should have only ONE imaginary frequency. 

It would be odd if a single TS could lead to different products. How would
the TS distinguish between paths to follow. I suspect that attempting to
rationalise some mathematical result will be academic. I doubt if it has any
physio/chemical meaning and is probably just the result of computation.
Simple finding some computational result does not mean anything. Results
should be reconciled with real-world problems.

James

-----Original Message-----
From: Sofia Godinho [mailto:[email-masked]]
Sent: Wednesday, June 06, 2001 6:43 PM
To: CCL
Subject: CCL:nth-order saddle point, n>1

Dear CCLers,
I wonder what is the chemical/physical meaning of a nth-order
saddle point (n>1)?
That is...for instance, when I get four immaginary frequencies
does it mean that I have to "pass through" four vibrational modes
to arrive to a minimum? (Or to three to get to a transition state?)
Or it simply has nothing to do with it and it is only a mathematical
definition of a saddle point?
Or...?

May I thank you in advance for any help, 
	Sofia

Sofia Godinho
Ph-D student
ITQB-UNL-Portugal
email: [email-masked]

-= 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: Christoph van Wüllen <[email-masked]>
Date: Thu, 7 Jun 2001 14:29:45 +0200

>A transition state should have only ONE imaginary frequency.
the reason is that if it is a higher-order TS, there will be another one
with lower energy, and molecules are sharp enough to take that one.
-- 
+---------------------------------+-------------------------------------+
| Prof. Christoph van Wullen      | Tele-Phone (+49) (0)30 314 27870    |
| Technische Universitat Sekr. C3 | Tele-Fax   (+49) (0)30 314 23727    |
| Strasse des 17. Juni 135        | eMail                               |
| D-10623 Berlin, Germany         | [email-masked]    |
+---------------------------------+-------------------------------------+