[QE-users] limit to take U value for DFT+U calculation

[Matteo Cococcioni]

Dear Rohit,

you could compute the value of U, for example using the linear-response,
DFPT-based hp.x code now included in QE. In the directory HP you will find
several examples on how to do that. Details about the implementation can be
found in PRB 98, 085127 (2018), arXiv:1805.01805v1 and references quoted
therein.

Best regards,

Matteo


Il giorno ven 6 set 2019 alle ore 07:53 ROHIT DAHULE 18210068 <
rohit.dahule at iitgn.ac.in> ha scritto:

> Dear Q-E users
> I m trying to get the band gap for System Cu2SnS3 with DFT + U.
> I have done calculation PBE + U by Considering U = 4, 5 , 6 , 7, 9  upto
> 15 and with increasing U values, band gap for the system also  increases.
> Is there any specific limit for consideration of U value ?
>
>
> Input file
>
> -----------------------------------------------------------------------------------
> &CONTROL
>                        title = 'CTS'
>                  calculation = 'scf'
>                 restart_mode = 'from_scratch'
>                       outdir = './scratch'
>                   pseudo_dir = './'
>                       prefix = 'CTS'
>                    verbosity = 'high'
>                        nstep = 1000
> /
> &SYSTEM
>                        ibrav = 0
>                          nat = 12
>                         ntyp = 3
>                      ecutwfc = 80
>                      ecutrho = 640
>  lda_plus_u = .TRUE.
>     lda_plus_u_kind = 0
> Hubbard_U(1) = 15
> /
> &ELECTRONS
>             electron_maxstep = 100
>                  mixing_mode = 'plain'
>                  mixing_beta = 0.4
>                  mixing_ndim = 8
>              diagonalization = 'cg'
> /
> &IONS
>                 ion_dynamics = 'bfgs'
> /
> &CELL
>                cell_dynamics = 'bfgs'
> /
> ATOMIC_SPECIES
>    Cu   63.5460000000  Cu.pbe-dn-kjpaw_psl.1.0.0.UPF
>    Sn  118.7100000000  Sn.pbe-dn-kjpaw_psl.1.0.0.UPF
>     S   32.0650000000  S.pbe-n-kjpaw_psl.1.0.0.UPF
>
> ATOMIC_POSITIONS {crystal}
> Cu       0.609860025   0.554603242   0.014502826
> Cu       0.756853280   0.738042423   0.513837567
> Cu       0.445393448   0.390139697   0.514502899
> Cu       0.261956405   0.243147538   0.013839616
> Sn       0.090842876   0.093003410   0.494452226
> Sn       0.906995789   0.909160925   0.994450414
> S        0.060036047   0.768130605   0.387963060
> S        0.231871856   0.939963608   0.887965000
> S        0.886684205   0.601038738   0.879478677
> S        0.398964467   0.113313382   0.379479276
> S        0.537436346   0.292294346   0.880764475
> S        0.707707256   0.462560085   0.380765964
>
> K_POINTS {automatic}
> 5 5 5  0 0 0
> CELL_PARAMETERS {bohr}
>   12.820803911   0.000373966   0.017355449
>    6.411463480  11.102558326  -0.017368345
>   -2.152496468   3.728515202  12.101963487
>
> ----------------------------------------------------------------------------------------------------------
>
>
> Regards
> Rohit Dahule
>
>
> --
> Rohit Dahule
> M. Tech. Student
> Materials Science and Engineering
> IIT Gandhinagar
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