Pre-calculated Hessian

As a simple approximation of the vibrational spectrum, one can re-use the HESSIAN computed from a geometry optimization.

&CPMD
  VIBRATIONAL ANALYSIS IM
  RESTART WAVEFUNCTION COORDINATES HESSIAN
&END

As a result, we get:

 ****************************************************************
 HARMONIC FREQUENCIES [cm**-1]:

         -0.0001         -0.0001          0.0000          0.0000
          0.0000          0.0000       1509.8283       3677.5896
       3927.2126

 PURIFICATION OF DYNAMICAL MATRIX

 ****************************************************************
 HARMONIC FREQUENCIES [cm**-1]:

          0.0000          0.0000          0.0000          0.0000
          0.0000          0.0000       1639.6812       3677.3605
       4075.8779

But comparing to the results of the other calculations, you can see that the frequencies are in part somewhat different. If you already have done a geometry optimizations, it is however a great way to get an overview of what the real spectrum should look like, as the calculation is very fast.