# CCL: W:Calculation of displacements in vibrational normal modes with
MOPAC

Sent to CCL by: "Michael Schmuker" [schmuker... |-at-|
...chemie.uni-frankfurt.de]
Dear List,
having only fundamental knowledge in quantum chemistry, I'm a bit lost on
this one:
I want to calculate vibrational normal modes of small organic molecules
using MOPAC and the respective atom displacements for each of them. So far,
I use MOPAC with the FORCE keyword, which gives me the frequencies of the
vibrations and two matrices, the "Normal Coordinate Analysis" and the
"Mass-Weighted Coordinate Analysis".
Can anyone tell me how to get from there to the atom displacements (in
x,y,z coordinates) for each vibrational mode? How can I calculate something
like the example below from those matrices?
Frequency 1234.5
Atom1 0.002 0.012 -0.090
Atom2 -0.123 0.087 0.089
Frequency 3548.5
Atom1 0.004 0.003 0.020
Atom2 0.003 -0.014 0.089
...
Many thanks in advance!
Kind Regards,
Michael
Michael Schmuker
Beilstein Endowed Chair of Cheminformatics
University of Frankfurt
schmuker AT chemie uni-frankfurt de