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

[Stefaan Cottenier]

I have not much experience with band gaps, but it looks like 2.8 and  
3.2 eV are fairly identical values. I wouldn't expect better  
consistency with a method so rough as LDA+U. If you really want 3.2  
eV, adjust your U-value (increase/decrease it up to 1-2 eV). This is  
'fitting', however.

Stefaan


> 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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>



-- 
Stefaan Cottenier
Instituut voor Kern- en Stralingsfysica
K.U.Leuven
Celestijnenlaan 200 D
B-3001 Leuven (Belgium)

tel: + 32 16 32 71 45
fax: + 32 16 32 79 85
e-mail: stefaan.cottenier at fys.kuleuven.be


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