[CP2K-user] [CP2K:16490] IR spectm for NaCl under PBC

[Victor Volkov]

Dear colleagues:
here is the normal mode analysis I could manage by now for NaCl under PBC.

There is only one unit cell: previously, I reported that I could not 
configure CP2K to reproduce NaCl structure using multiple cells 2 2 2.
There are strange distortions, which I did confirm to sustain under 
different CUTOFF values (1000 and 600), and regardless if dispersion is 
switched off or not.

When a single cell under PBC, optimization leads to the “right” structure, 
when ESP 10^-12.

However, the negative(imaginary) frequencies are many and they are very 
large.
I may anticipate that the “miss performance” is enhanced due to the PBC.

Eventhough the results are "devastating",
:-)
nonetheless, I find this might be very good, very helpful – I got an idea.

Dear Dr. Hutter,
is it possible that CP2K may have an “issue” about positioning a structure 
in respect to both, in respect to the FT grind and in respect to the PBC.
Perhaps, there could be a relative mismatch phenomenon, which could 
stimulate artificial transition states with negative frequencies?

May be, what I observe is that PBC on the unit cell helps to sense this 
better?


Thank you for your time and for any comments.

With best regards,
Sincerely
Victor

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