[CP2K-user] [CP2K:17886] Vibrational analysis

[mengchao shi]

Dear JH
Thank you so much.

在2022年10月17日星期一 UTC+8 15:32:06<jgh> 写道：

> Hi
>
> adding to this correct explanation of the problem. Unfortunately, the 
> translational
> invariance will be broken more severely in CP2K (using the GPW method)
> than in other codes using equidistant grid integration. If you want to 
> reduce this effect
> in CP2K you need to run with the GAPW method or GPW with NLCC 
> pseudopotentials.
>
> regards
>
> JH
>
> ________________________________________
> From: cp... at googlegroups.com <cp... at googlegroups.com> on behalf of Lucas 
> Lodeiro <eluni... at gmail.com>
> Sent: Saturday, October 15, 2022 6:17 PM
> To: cp... at googlegroups.com
> Subject: Re: [CP2K:17871] Vibrational analysis
>
> Hello Mengchao,
>
> AFAIK your results are consistent. Of course there are 24 normal modes, 
> and 3 of them are translational ones. CP2K removes the translational modes 
> before printing the data, you can find this in the CP2K output (search 
> "VIB| Eigenvectors before removal" and " VIB| Frequencies after removal"), 
> where the complete set of normal modes and frequencies are printed before 
> the translational removal. This does not change significantly the results, 
> so you can think about 21 normal modes and 3 extra translation modes with 
> zero frequency.
> In VASP the translational removal is not done and the low frequency modes 
> are the translational ones... but at Gamma point they must be zero 
> frequency. The resulting non zero value is an artifact of the PW rupture of 
> translational invariance, which is due to the non complete PW basis set 
> (infinite energy plane wave). As a guess, taking into account that in VASP 
> the PW cutoff is lower compared with used in CP2K, and PW are used to 
> wavefunctions, the error due to rupture of translational invariance is 
> higher in VASP.
>
> Regards - Lucas
>
> El vie, 14 oct 2022 a las 0:42, mengchao shi (<smclu... at gmail.com<mailto:
> smclu... at gmail.com>>) escribió:
> Dear all
> I want to calculate the atomic frequency of diamond silicon by CP2K.
> My supercell contains N=8 atoms (a PBC system), and I will get the 3N=24 
> frequencies.
>
> However, I only get the 21 frequencies, The frequencies of the rotations 
> are obtained, but the part of translations are not obtained.
>
> I use the VASP to calcualte the vibrational analysis, I get the 24 
> frequencies.
> I compare the two results:
>
> VASP: (unit: cm-1, 24 frequencies )
> 513.100912 513.097046 513.092040
> 461.327377 461.230874 461.217489 461.210747 461.189027 461.185948
> 409.422422 409.414429 409.406072 409.397086 409.393930 409.387741
> 140.194017 140.189188 140.187673 140.182783 140.175562 140.172242
> 0.006451 0.010431 0.055547
>
> CP2K: (unit: cm-1, 21 frequencies)
> 515.944308 515.944308 515.944308
> 463.042397 463.042397 463.042397 463.042397 463.042397 463.042397
> 412.993772 412.993772 412.993772 412.993772 412.993772 412.993772
> 139.536054 139.536054 139.536054 139.536054 139.536054 139.536054
>
> The results are similar, but the number is different, how do I get 24 
> frequencies by CP2K.
>
> The part input:
> "
> &GLOBAL
> PROJECT system
> RUN_TYPE VIBRATIONAL_ANALYSIS
> PRINT_LEVEL MEDIUM
> &END GLOBAL
>
> &VIBRATIONAL_ANALYSIS
> NPROC_REP 3
> DX 0.001
> FULLY_PERIODIC .TRUE.
> &END VIBRATIONAL_ANALYSIS
> "
>
> Thank you for your help.
> Best,
> Mengchao.
>
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