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

[ROHIT DAHULE 18210068]

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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