Rasha
While one 'could imagine some way to compute IR and/or Raman intensities
using classical mechanics force fields, there are many papers that show
that most of the solutions are very wrong.
Basically, for IR you need the change in dipole moment with a normal
mode coordinate, and for Raman you need the change in polarizibility
with a normal mode coordinate.
Since classical force fields like amber do not change charges when you
change conformations, the only change in dipole moment or polarizibility
comes from changing the coordinates, which is NOT enough to predict
intenstities with any accuracy.
Adrian
On 5/8/13 11:51 AM, Rasha Alqus wrote:
> Dear Amber Users,
>
>
>
> I have used normal mode function in nab to calculate the Raman frequency using normal mode analysis (see the input file input.nab), i have obtained two files the first is vecs file which contain the (normal mode, frequency , coordination) and second that contain energy.
>
> I would like to obtain the intensity of each frequency in order to plot (frequency vs. intensity) as in Raman spectrum, is there a method to obtain these intensity? or are already present in some line in the second file? is my input.nab file correct or i have missed some point in it?
>
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> Kind Regards
>
> Rasha
>
>
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--
Dr. Adrian E. Roitberg
Professor
Quantum Theory Project, Department of Chemistry
University of Florida
roitberg.ufl.edu
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Received on Wed May 08 2013 - 11:00:03 PDT
