[CP2K-user] [CP2K:17584] Re: Recreating VASP results - CuO PBE+U - Terrible results

[mdsimula...@gmail.com]

To summarize what is wrong, the cell A side is too long, the cell B side is 
too short and the band gap is too small.

I'm using a 3x3x3 multiple unit cell and a U_MINUS_J 3.0

I'm currently running U_MINUS_J 0.0 and a small unit cell with only KPOINTS.

The experimental cell values: 
ABC 4.653 3.410 5.108
ALPHA_BETA_GAMMA 90.00 99.48 90.00

The values I'm getting with:
ABC 4.846 3.208 5.172
ALPHA_BETA_GAMMA 90.00 94.526 90.00

The HOMO-LUMO gap from CP2K (using PRINT/MO/EIGENVALUES) is 0.96 eV and the 
reported value ~1.3 eV.

Anyone got any ideas???
On Monday, August 29, 2022 at 11:38:43 AM UTC-4 mdsimula... at gmail.com wrote:

> Hello,
>
> I have been trying to recreate a VASP calculation of CuO in CP2K 7.1 (I'm 
> working on compiling CP2K 2022.1) with poor results.  I've also seen this 
> calculation using Quantum Espresso with good success too.
>
> The calculation uses PBE+U and I'm using broken symmetry to set up the 
> antiferromagnetic spins. 
>
> In the paper (https://pubs.acs.org/doi/10.1021/acs.jpcc.5b10431), they 
> are able to get pretty good agreement with the experimental geometry (Table 
> 1) even without the +U but regardless of my +U value, the optimized cell is 
> terrible and the band gap is too low.
>
> I have tried different U_MINUS_J values, 0 to 5, and 3 seems to be the 
> "best".  The high values lead to instability. I've also tried without 
> broken symmetry but results are inconclusive (I need to play with this 
> more).
>
> Does anyone have any suggestions on why the calculation might be giving 
> odd/wrong results?
>
> My input, xyz coordinates, and output are attached.
>
> If more information on my end is needed, please don't hesitate to ask.
>
> This has been troubling me for a month now so any help would be greatly 
> appreciated! 
>
> Best regards,
> Frank
>

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