[QE-users] Regarding band calculation of BiFeO3

[Srihari Venugopala Rao]

Dear all,
                  I have been working on bismuth ferrite BiFeO3, from past
few months.
I use NC pseudopotential from pseudodojo and made all the optimization with
respect to cutoff energy, K-points before performing the calculations.
The band calculation shows no bandgap (it has a bandgap of about 2.67 eV),
hence calculations like Berry phase, dielectric and Turbo Lanczos and
others cannot be performed as it is predicted to be a metal.
I solved the bandgap issue with the implementation of Hubbard potential (up
to U= 5 eV for Fe), but this does not solve the issue completely as few of
the calculations do not have the implementation of Hubbard potential in
them. I wanted to know whether I am making any mistake or is there any
workaround so that I can perform the dielectric property calculations for
my material. I am pasting the scf input file if it is of any use. Thanks in
advance

/* Input file*/
&CONTROL
    calculation = "scf"
restart_mode = 'from _scratch"
    max_seconds =  8.64000e+04
    pseudo_dir  = "."
    tprnfor     = .TRUE.
prefix      = "BFO"
    outdir      = "./outdir"
    tstress     = .TRUE.
/

&SYSTEM
    a                         =  5.645
    cosab                     =  0.50000
    degauss                   =  1.00000e-02
    ecutrho                   =  9.60000e+02
    ecutwfc                   =  8.00000e+01
    ibrav                     = 5
    nat                       = 10
    nspin                     = 2
    ntyp                      = 3
 lda_plus_u                =.true
    Hubbard_U(1)              =2.0
    occupations               = "smearing"
    smearing                  = "gaussian"
    starting_magnetization(1) =  2.00000e-01
    starting_magnetization(2) =  0.00000e+00
    starting_magnetization(3) =  0.00000e+00
/

&ELECTRONS
    conv_thr         =  1.00000e-09
    electron_maxstep = 200
    mixing_beta      =  4.00000e-01
    startingpot      = "atomic"
    startingwfc      = "atomic+random"
/

K_POINTS {automatic}
 8  8  8  0 0 0

ATOMIC_SPECIES
Fe     55.84500  Fe.UPF
Bi    208.98038  Bi.UPF
O      15.99940  O.UPF

ATOMIC_POSITIONS (crystal)
Fe       0.777130455   0.777130455   0.777130455
Fe       0.277129455   0.277129455   0.277129455
Bi       0.509340660   0.509340660   0.509340660
Bi       0.009340660   0.009340660   0.009340660
O        0.563857130   0.956239313   0.116400442
O        0.956239313   0.116400442   0.563857130
O        0.116400442   0.563857130   0.956239313
O        0.616401442   0.456238313   0.063856130
O        0.456238313   0.063856130   0.616401442
O        0.063856130   0.616401442   0.456238313
/* end of input file */


Regards,
Srihari
Research scholar
Department of Physics
Manipal Institute of Technology
Manipal
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