[CP2K-user] [CP2K:16634] IR spectrum. Help wanted.

[Sam Broderick]

Martin Brehm suggested avoiding Wannier localization and to use Voronoi 
(see spec_tutorial_2018.pdf 
<https://brehm-research.de/files/spec_tutorial_2018.pdf>). Unfortunately 
this is for a fairly large liquid (R)-propylene oxide cell with 320 atoms.

Currently, I am trying to rework this tutorial for methanol to get a 
feeling for TRAVIS.

In the tutorial linked above, Martin writes:

"The “&PERIODIC_EFIELD” section controls the external electric field which 
you will need to
apply for Raman and ROA spectra. The intensity is specified in atomic 
units. In the tutorial,
we use a value of 5 · 10 −3 a.u. = 2.57 · 10 9 V m −1 , which we found to 
be a good compromise.
Too small values lead to noisy spectra, whereas too large values might 
leave the linear regime
of electronic polarizability."

On Wednesday, February 23, 2022 at 4:36:14 PM UTC+1 tkuehne wrote:

> Please also check if the Wannier localization has ALWAYS converged. 
> In that respect the JACOBI approach is the most robust. 
>
> Best, 
> Thomas Kühne
>
> Am 23.02.2022 um 15:25 schrieb Sam Broderick <wave... at gmail.com>:
>
> See fawzi's post on Oct 20, 2010, 1:38:58 PM: Problems of IR and dipole 
> calculation
>
> He recommends looking at the Wannier Center movement and consider 
> centering.
>
> On Wednesday, February 23, 2022 at 2:14:52 PM UTC+1 Sam Broderick wrote:
>
>> Dear IR-Colleague
>>
>> 6'000 or 60'000? If it is 6'000, that would be the reason.
>>
>> Otherwise, what were your TRAVIS inputs?
>>
>> Rgds
>> Sam
>>
>> On Wednesday, June 30, 2021 at 1:31:29 PM UTC+2 zsh1... at gmail.com wrote:
>>
>>> Hello everyone,
>>>
>>>  I am trying to do vibrational analysis for gas phase system. I am 
>>> following the tutorial "Calculating Vibrational Spectra from Molecular 
>>> Dynamics". Initially i have done massive equilibration of a single methanol 
>>> system for 6000 steps. After that i use the following example CP2k input 
>>> file to simulating a trajectory with wannier centers for 60000 steps. 
>>> Then, I calculated the IR spectra with methanol_wannier.xyz file using 
>>> Travis software. Unfortunately, I don’t get a good IR spectrum because of 
>>> it doesn’t show peaks at 200, 1000, 1500 and 3700 cm-1 and it has very 
>>> noise. Would you please guide me why I don’t get a good IR spectrum?
>>>
>>>
>>> Here i am attaching my IR spectrum and the input files of massive 
>>> equilibration and the wannier center for a single methanol.
>>>
>>> Please help me on this.
>>>
>>> Thanks.
>>>
>>> [image: IR.png]
>>>
>>
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> ==============================
> Thomas D. Kühne
> Dynamics of Condensed Matter
> Chair of Theoretical Chemistry
> University of Paderborn
> Warburger Str. 100
> D-33098 Paderborn
> Germany
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