[Wien] some questions about LDA+U caculation of anatase

[Saeid Jalali]

It  is generally believed that the on-site Coulomb repulsion U integral as an input  parameter for the LDA+U calculations depends on the system under study, and can  vary for an atom from one case to the others.  Furthermore, the value obtained for the U parameter depends on the method of  calculations.
  Thus one can first calculate a suitable U value for each case using the  method discussed by Anisiomov 91 (PRB). An alternative way is to vary  the U value in a proper interval to find the most appropriate one  comparing the theoretically calculated results with the experiment.
  
  It is mandatory to set the U value (effective one,i.e. U-J) for each  nonequivalent atoms. But I see in your struct file you have two  equivalent Ti atoms. Hence for your case only one U_effective is  necessary in your inorb file.
  
°×Óî <baiyu1982 at ss.buaa.edu.cn> wrote:  Dear Wien users:
Recently I had done some caculation about anatase TiO2 using LDA+U method. I followed Anisimov's way that add a 6eV potential
to Ti 3d orbit. But I could not get the correct result like his caculation which have a 3.2eV bandgap, while I have only 2.8eV.
Since  he is using the LCAO basis, I wondered whether his U=6eV is suitable  for out LAPW basises? Major input file is listed below.And at the same  time I want to know whether the two Ti atoms in struct file which all  have the same atom index have been added with the orb potential?
Please give me some suggestions on how i can get a more desirable result like a 3.2 eV bandgap?

PS: my SCF is ran under -ec 0.00005. Is the covergence too large?


anatase
B   LATTICE,NONEQUIV.ATOMS:  2141_I41/amd
MODE OF CALC=RELA unit=bohr
  7.223948  7.223948 18.164868 90.000000 90.000000 90.000000
ATOM  -1: X=0.00000000 Y=0.25000000 Z=0.87500000
          MULT= 2          ISPLIT=-2
      -1: X=0.00000000 Y=0.75000000 Z=0.12500000
Ti         NPT=  781  R0=0.00005000 RMT=    1.8000   Z: 22.0
LOCAL ROT MATRIX:    0.7071068-0.7071068 0.0000000
                     0.7071068 0.7071068 0.0000000
                     0.0000000 0.0000000 1.0000000
ATOM  -2: X=0.00000000 Y=0.25000000 Z=0.08271596
          MULT= 4          ISPLIT= 8
      -2: X=0.00000000 Y=0.75000000 Z=0.91728404
      -2: X=0.00000000 Y=0.75000000 Z=0.33271596
      -2: X=0.50000000 Y=0.75000000 Z=0.16728404
O          NPT=  781  R0=0.00003000 RMT=    1.6000   Z:  8.0
LOCAL ROT MATRIX:    1.0000000 0.0000000 0.0000000
                     0.0000000 1.0000000 0.0000000
                     0.0000000 0.0000000 1.0000000
  16      NUMBER OF SYMMETRY OPERATIONS
******************************************************************
indm:
-9.                      Emin cutoff energy
 1                       number of atoms for which density matrix is calculated
 1  1  2      index of 1st atom, number of L's, L1
 0 0           r-index, (l,s)index
*********************************************************************
inorb:
  1  1  0                     nmod, natorb, ipr
PRATT  1.0                    BROYD/PRATT, mixing
  1 1 2                          iatom nlorb, lorb
  1                              nsic 0..AFM, 1..SIC, 2..HFM
   0.44 0.01                      U J (Ry)
 
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Sincerely yours,
S. Jalali.
/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/
Saeid Jalali Asadabadi,
Department of Physics, Faculty of Science,
University of Isfahan (UI), Hezar Gerib Avenue,
81744 Isfahan, Iran.
Phones:
Dep. of Phys.      :+98-0311-793 2435
Office             :+98-0311-793 2430
Fax No.            :+98-0311-793 2409
E-mail             :s_jalali_a at yahoo.com
www                :http://www.ui.ac.ir
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