From owner-chemistry.,at,.ccl.net Wed Jun 20 14:08:01 2007
From: "Gustavo Seabra gustavo.seabra^_^gmail.com" <owner-chemistry[a]server.ccl.net>
To: CCL
Subject: CCL:G: Fixing distance between point charge and atoms
Message-Id: <-34529-070620115902-24961-qA9v7MuNM4xnCzcTXoRekQ[a]server.ccl.net>
X-Original-From: "Gustavo Seabra" <gustavo.seabra~!~gmail.com>
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Date: Wed, 20 Jun 2007 11:03:54 -0400
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Sent to CCL by: "Gustavo Seabra" [gustavo.seabra:-:gmail.com]
You can try adding an additional electron-repulsive term to the point
charge, as described in the Gaussian webpage:

http://gaussian.com/g_ur/k_charge.htm

HTH,

Gustav Seabra.
 

> -----Original Message-----
> From: owner-chemistry%%ccl.net [mailto:owner-chemistry%%ccl.net] 
> Sent: Wednesday, June 20, 2007 12:39 AM
> To: Seabra,Gustavo 
> Subject: CCL:G: Fixing distance between point charge and atoms
> 
> 
> Sent to CCL by: "Chunyi  Sung" [juneyi1(~)yahoo.com.tw] Hi, CCLers
>  
>       I am trying to optimize some molecules in the presence 
> of point charges using the keyword "charge" in Gaussian; 
> however, in my case, some O atom in the molecule always ended 
> up colliding with a positive point charge during geometry 
> optimization. Therefore, I want to somehow set up some 
> constraints on that O atom so that it will stay, say, 2.7 
> Angstrom away
> > from the positive point charge, does anyone know how to do that ?
> 
>       Originally, I wanted to put a ghost atom right at the 
> location of the positive point charge, and then use 
> "modredundant" to fix the bond length between the O atom and 
> the ghost atom. However, with the "charge" keyword to include 
> point charges, "Opt" must have "Z-matrix", which does not 
> work with "modredundant". So I am now running out of ideas. 
> I'll appreaciate if anybody has any suggestions on this. 
> 
> thanks
> 
> chunyi