Subject: [Summary]:IR intensity

From: 川島 武 <[email-masked]>
Date: Tue, 18 Apr 1995 08:29:00 +0900

On Date: Thu, 06 Apr 1995 08:28:00 +0900, I posted the question about the
IR intensity calculation.
Some kind souls have sent me the comments. Here I thank them very much.
The summary follows the original question.

---
>>Dear CCL'ers
>>
>>We are trying to determine the orientation of the adsorbed molecules on 
>>the surface by IR using polarized light. It seems to be possible to 
calculate
>>the intensity from each component of dipole moment derivetives, but are
>>there any programs that can do this automatically or rather easy way?
>>We have gaussian.
>>
>>Thanks in advance.

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Date: Wed, 5 Apr 1995 21:53:00 -0400 (EDT)
From: Cheol Choi <[email-masked]>

You can easily get the dipole moment derivatives from gaussian program.

If you do frequency calculation, you will find a lot of numbers at the
end of output files.

After the kerword "DipolDeriv", you will have dipole derivative w.r.t
cartesian coordinate.

However, if you want to calculate IR intensity using it,
you need also transformation matrix to normal coordinates.

Best wishs Cheol-Ho,
Georgetown Univ.

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Date:         6 Apr 95 09:20:20 GMT
From: Dave <[email-masked]>

I may have misunderstood your problem but the following would seem to
pose a problem...

How do you propose to carry out a Gaussian calculation for such a
complexed system. I thought that such ab initio approaches were
usually only applicable to small isolated systems.

A better appraoch might be to try and model the adsorbed system using
a MM force field which has been optimised for the prediction of
vibrational frequencies and dipole moments. I believe MM3 and CFF91
do this quite well.

In my work I trying to do reliable vibrational simulation using a
velocity autocorrelation on MD data. We are doing this using the
dynamics module under Cerius2 (by MSI). The parameter sets still need
tweaking a bit though. In Cerius2 you can split the VAC and power
spectrum into its anisotropic components I am not sure if this is
what you want.

Perhaps you should contact MSI to find out exactly what the
significance of these axially resolved power spectra are.

Regards

David Tilbrook
**********************************************************
David Tilbrook              *   Tel: 44 1483 300 800 x 9591
Polymer Group,              *                        x 2617
Chemistry Department,       *
University of Surrey,       *   Fax: 44 1483 259 514
Guildford, Surrey, GU2 5XH  *
U.K.                        *
**********************************************************

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Date: Thu, 6 Apr 1995 10:59:50 +0200 (SAST)
From: Magan Govender - PG <[email-masked]>

Dear Sir,
As far as I am aware most programs perform
a complete normal coordinate analysis requiring
the dipole moment derivatives, which are summed 
and multiplied by a constant to give the intensities,
bearing in mind the signs for each component. Some
of the programs are Vibra by Dr.Steele, NCA, SPECTRO.
I have the email addresses of the authors, if required
I shall be pleased to forward them to you.

Greetings from South Africa
Magan

______________________________________________________________________

M.G. Govender
Centre for Theoretical and Computational Chemistry
Dept of Chemistry
University of Natal
King George V Avenue
Durban                              
South Africa                                                          
 
---
 It seems to me that your idea is OK to first order; however, in order
to get the IR adsorption lineshapes and the relative intensities
correct, I think you'll need to consider the substrate-adsorbate
interactions.  What kind of surface are the molecules adsorbed onto?

Eric R Bittner
Univ. of Texas at Austin