help, how to use DFT+U

[Marco]

Hello,

Depending on your system, it may not be necessary to use the U_RAMPING 
method. I was able to reproduce experimental surface energies from slab 
calculations for certain systems consisting of first-row transition metal 
atoms without using the U_RAMPING method. The paper by Dr. Matthias Krack 
on uranium oxide in which he used the U_RAMPING method is considered a more 
challenging system than first-row TM systems. Try running the calculations 
without U_RAMPING. Also, of your structure is not reasonable, that would 
also cause problems.

Regards,
Marco

On Tuesday, April 1, 2014 10:40:09 PM UTC-4, roben nano wrote:
>
> Hi all,
>
> I am using DFT+U to relax a defective surface system. Specifically, I am 
> using theDFT+U method MULLIKENn. However, the following warning appears 
> when computing:
>
> *** 04:19:11 WARNING in dft_plus_u:mulliken :: DFT+U energy contibution ***
>  *** is negative possibly due to unphysical Mulliken charges. Check your 
> ***
>  *** input, if this warning persists or try a different method!    
> - I try to converge the initial SCF run with U=0eV firstly and then try to 
> restart with DFT+U. but the same problem appears.
> - Using U_RAMPING [eV] 0.1 and INIT_U_RAMPING_EACH_SCF did not help.
> ............
>     &KIND Zn
>     BASIS_SET DZVP-MOLOPT-SR-GTH
>     POTENTIAL GTH-PBE-q12 
>      &DFT_PLUS_U
>         EPS_U_RAMPING 1.0E-3
>         U_MINUS_J [eV] 2.0
>         L 2
>         U_RAMPING [eV] 0.7
>       &END DFT_PLUS_U
>    &END KIND
> ..................................
> Thanks a lot for the attention,
> best regards,
>
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