CCL:G: Raman spectra using QM/MM

 Sent to CCL by: Peter Burger [burger^chemie.uni-hamburg.de]
I would suggest to have a look at Turbomole ver. 5.10 which offers _analytical_ Raman intensities. Including the very fast RI DFT methods even sizable molecules are amenable for these calculations without the need for ONIOM unless we are talking about proteins. 
 Just worth my .01 cents
 Peter
 Steve Williams willsd]|[appstate.edu schrieb:
 
 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
Sincerlyhttp://www.ccl.net/chemistry/sub_unsub.shtmlConferences: 
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 Prof. Dr. Peter Burger
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