Subject: MOLECULAR MECHANICS CALC OF IR SPECTRA

From: elewars <[email-masked]>
Date: Tue, 22 May 2001 12:51:22 -0400

2001 May 22

Hello,

    Molecular mechanics programs can now calculate the positions
(cm**-1) of normal-mode vibrations. However, MM by itself cannot
calculate the _intensities_ of these vibrations, since this depends on
the change in dipole moment, which in turn depends on electron
distribution, a concept outside MM theory.

    It seems, however, that in principle MM could calculate intensities
using assigned bond moments or atom charges, which would provide a rapid
way of calculating IR spectra. Has this been implemented in any program?

Thanks

E. Lewars
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