[CP2K-user] [CP2K:16503] Re: IR spectm for NaCl under PBC

[Victor Volkov]

Dear Dr.Hutter
good moring in Milchbuck

>For k-point calculations the dipoles are not available and no IR
intensities are possible.
>In addition you only get the Gamma point phonon.

Thank you for the kind answer.

> For systems like NaCl, what you usually want is a full phonon spectra.

I target normal modes in LixMnyOz systems to explain
changes of Raman modes at cathode of en electric element
upon a phase transitions, which i could induce using a laser field.
NaCl is a test ground to understand.

>you should use specialized software like phonopy that interfaces to CP2K
(and many other codes).

Jein: Yes, and No.

I installed and run phonopy under cygwin-windows.
Indeed, usinf CP2K,
phonopy does compute phonon DOS and PDOS.

However, a scientific discussion requires understanding what kind of
interatomic displacements
those densities would correspond.
In this respect,
learning how to condition cp2k is the only way
towards practical.

Just to have DOS from phonopy and normal modes from cp2k,
already would be a sufficient playground to impact technology.

However, conditioninig cp2k to generate relevent (no need to be perfect)
normal modes
is the important connection.

After 30 years in spectroscopy,
I may say that even computing IR or Raman may not be that important.

Yes, computing such is possible using, for example:
git clone https://github.com/JMSkelton/Phonopy-Spectroscopy.git


However, IR-Raman is  just a "luxury".

Correlating normal modes to phonon DOS is sufficient to answer many
questions

With best regards,
Victor













On Wed, Jan 26, 2022 at 12:26 PM <hutter at chem.uzh.ch> wrote:

> Hi
>
> The vibrational analysis module is most useful for molecular systems
> (molecular crystals) calculated at the Gamma point. In this case
> you can also calculate IR intensities through dipole derivatives.
> For k-point calculations the dipoles are not available and no
> IR intensities are possible. In addition you only get the
> Gamma point phonon.
> For systems like NaCl, what you usually want is a full phonon spectra.
> In this case you should use specialized software like phonopy
> that interfaces to CP2K (and many other codes).
>
> regards
>
> Juerg Hutter
> --------------------------------------------------------------
> Juerg Hutter                         Phone : ++41 44 635 4491
> Institut für Chemie                E-mail: hutter at chem.uzh.ch
> Universität Zürich
> Winterthurerstrasse 190
> CH-8057 Zürich, Switzerland
> ---------------------------------------------------------------
>
> -----cp2k at googlegroups.com wrote: -----
> To: cp2k at googlegroups.com
> From: "Victor Volkov"
> Sent by: cp2k at googlegroups.com
> Date: 01/25/2022 05:14PM
> Subject: Re: [CP2K:16499] Re: IR spectm for NaCl under PBC
>
> Dear Fabian:
> sorry to bother once more.
>
> Learning from your comments, I optimized the structure (please, see the
> attached outut)
> under
>     MAX_DR    8.0E-06
>     RMS_DR    4.0E-06
>     MAX_FORCE 1.0E-06
>     RMS_FORCE 1.0E-07
>
> This is to run vibrational analysis using the input, as attached.
>
> In DFT, I do instruct to prinnt moments (as you may see),
> but
> CP2K reports an error- to be unable to read the moments.
>
> I wonder if such unexpected "blindness"
> is present because the input contains
>    &KPOINTS
>    SCHEME  MONKHORST-PACK  8 8 8
>    FULL_GRID  .TRUE.
>    &END KPOINTS
>
> I include this definition trying to acount the Brullion space structure.
> May be this is outside of the scope.
>
> I wish to understand a bit how CP2K vibrational analysis
> accounts (or not) dfinitions of
> multiple cell, k-points and periodicity.
>
> I be thankful if you comment.
> Victor
>
>
> On Mon, Jan 24, 2022 at 7:02 PM Victor Volkov <volkovskr at gmail.com> wrote:
> Dear Fabian;
> excellent!
> Great learning.
> Thank you.
> With best regards,
> :-)
> Victor
>
> On Mon, Jan 24, 2022 at 4:22 PM fabia... at gmail.com <fabianducry at gmail.com>
> wrote:
> Dear Victor,
>
> You need a much tighter convergence criterion for the optimization prior
> to the vibrational analysis. You increased  MAX_FORCE to 5e-3 (guessing
> from the output), instead you have to decrease it to at least 1e-5, maybe
> even lower.
> CP2K prints the forces for the replica in the output. The forces under
> "Minimum Structure - Energy and Forces:" should be more or less 0 and
> considerably differ between the other images. Currently you are computing
> the vibrational analysis from almost pure noise.
>
> Cheers,
> Fabian
> On Sunday, 23 January 2022 at 19:58:05 UTC+1 volk... at gmail.com wrote:
> 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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> [attachment "NaCl_1GPWdiag.out" removed by Jürg Hutter/at/UZH]
> [attachment "NaCl_1GPWdiag_F.inp" removed by Jürg Hutter/at/UZH]
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