[CP2K-user] [CP2K:18770] VIBRATIONAL ANALYSIS

[Lucas Lodeiro]

I put my 2 cents in the possibility that you are running your calculation
using PBC, so the normal modes are not projected out to extract the
translational and rotational modes. Also you probably use a "low cutoff" so
the noise (energy/gradient waves due to plane waves), when the numerical
derivatives are calculated through adjacent points, is important... then
the frequency of your translational and rotational modes are not close to
zero as expected.

Regards - Lucas Lodeiro

El jue, 4 may 2023 a las 12:36, Hana (<holiaei2 at illinois.edu>) escribió:

> Hello,
>
> I am trying to obtain the normal modes of my gaseous system which contains
> a molecule (N atoms). First I optimize the geometry of my system with a
> MAX_FORCE threshold of 0.0005. Second, in a further calculation, I use the
> following setting:
>
> &VIBRATIONAL_ANALYSIS
>   INTENSITIES
>   NPROC_REP 256
>   DX 0.001
>   &PRINT
>     &PROGRAM_RUN_INFO ON
>     &END
>   &END
> &END
>
> I get 3N frequency modes all of which are nonzero. However, I expect the
> analysis to exclude the rotation and translation and return zeros for the
> first six modes. Is there any explanation for this? Here is the output
> (cm^-1) for the first six modes: 26.89, 30.12, 36.90, 55.93, 68.51, 90.65
>
> Thanks!
>
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