In general, calculations of
vibrational frequencies (normal mode analyses) provide the frequencies
themselves (as the square roots of the eigenvalues), but also the atomic
displacements involved in each mode (from the eigenvectors), which tell us
what each separate vibrational motion looks like.
Typically a calculation will print out
the frequency of each vibrational normal mode, and the associated atomic
displacements.
For example, for the water molecule calculation, the optimized Cartesian coordinates are:
|
Centre |
Atomic |
Atomic coordinates |
||
|
number |
number |
X |
Y |
Z |
|
1 |
8 |
0.000 |
0.000 |
0.127 |
|
2 |
1 |
0.000 |
0.758 |
-0.509 |
|
3 |
1 |
0.000 |
-0.758 |
-0.509 |
The molecule lies in the YZ plane.