[CP2K-user] [CP2K:11082] comparing CP2K-DFTB (5.1) and DFTB+ (18.2)

[Thomas Kühne]

Dear Maxime, 

your input files looks good to me. 
How large is the difference in the 
periodic cases? 

Merry Christmas, 
Thomas

> Am 22.12.2018 um 22:45 schrieb Maxime Van den Bossche <maxime.cp.v... at gmail.com>:
> 
> Hi all,
> 
> I also did a quick comparison now between CP2K and DFTB+
> for a simple rocksalt MgO structure (8 atoms in total,
> using the OT minimizer in CP2K). The input and output 
> files for both codes are attached. 
> 
> What I found so far:
> 
> * Without periodicity, the two codes agree quite well
>   in terms of the H0 and SCC energies (up to ~1e-4 Ha)
>   as well as the Mulliken charges.
> 
> * In the periodic case, so far I haven't managed to
>   get comparable results with the two codes. The CP2K
>   results indeed appear sensitive to the choice of the 
>   Ewald alpha parameter, similar to what Wei observed.
>   For each of the three ALPHA values I tried, the resulting
>   energies and SCC charges are quite different from DFTB+.
> 
> * In contrast to Wei, though, I also get different results
>   for both codes in non-self-consistent calculations
>   (but at least here the CP2K results indeed no longer
>   depend on ALPHA).
> 
> It would be great if you could check whether my CP2K
> inputs have been appropriate. If so, I hope this example will
> help to get to the bottom of this.
> 
> Best,
> Maxime
> 
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> <files.zip>

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