From owner-chemistry@ccl.net Wed Jun 18 16:08:00 2008
From: "Steve Williams willsd]|[appstate.edu" <owner-chemistry()server.ccl.net>
To: CCL
Subject: CCL:G: Raman spectra using QM/MM
Message-Id: <-37184-080618151655-21337-9aI+TdHefOa3avoPRmHMNQ()server.ccl.net>
X-Original-From: Steve Williams <willsd-,-appstate.edu>
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Date: Wed, 18 Jun 2008 14:17:41 -0400
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Sent to CCL by: Steve Williams [willsd^_^appstate.edu]
Raman intensities are available in G03, but since they require numerical 
derivatives for MP2 and DFT methods they are very slow to compute and by 
default they are not calculated on a frequency job.  If you change your 
input to include freq=raman on the route line, they will be computed.  
Six separate calculations will be done for each atom (+/- displacements 
in x, y, z) to compute the needed polarizability derivatives.  You can 
estimate how long this will take by doing a single point polarizability 
calculation then multiplying the time required for this by 6*N where N 
is the number of atoms in your molecule (the portion you want to compute 
with b3lyp).

Caveat:  While I have computed LOTS of Raman spectra with Gaussian, I 
have not combined this with an ONIOM calculation.... maybe it does not 
work at all with ONIOM.

BTW: If you include the first 20 or so lines of your input file when 
posting a question like this, you are more likely to get useful 
answers.  For example I am just assuming that you did not specify 
freq=raman.

Steve Williams


Workalemahu Mikre Berhanu wberhanu|*|mail.ucf.edu wrote:
> Sent to CCL by: "Workalemahu Mikre Berhanu" [wberhanu|,|mail.ucf.edu]
>
> I was trying to use the QM/MM method for calculating the raman intensities using gauss view for linux. In the literature there are reports which show it is possible to do Raman intensity calculation using gaussuian. Could you please provide me information on how I could solve my problem? I have tried  ONIOM(b3lyp:amber), ONIOM(b3lyp:uff) and  ONIOM(b3lyp:dreiding) but I could not get the raman intensities.
>
>
> Thank you
>
> Sincerly>
>
>