help, how to use DFT+U

[roben nano]

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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