[Wien] How to get accurate GAP using BJ or mBJ methods?

tran at theochem.tuwien.ac.at tran at theochem.tuwien.ac.at
Mon Feb 29 18:40:25 CET 2016


The fundamental problem of DFT is to be an approximate method whatever
is the xc functional/potential that is used.

Anyway, if you really need band structure for your compounds with correct
band gap, then you can empirically adjust the parameter c of the mBJ
potential until the desired band gaps is obtained. For this, you need
to create the file case.in0abp.
For instance if you want to fix c to 1.2, the case.in0abp should be like
this (see Sec. 4.5.9 of the UG):
1.2
0.0
1.0

F. Tran

On Mon, 29 Feb 2016, JingQun wrote:

> 
> Dear all,
> 
> I am running wien 14.2 on a machine with operating system centos 6.5, fortran compiler ifort.
> 
> I want to calculate the electronic structures of borates (such as BBO, KBBF, LBO, and so on)and get accurate GAP using BJ or mBJ methods. During the calculation, I have encountered some problems. They are:
> 
> 1, Take KBBF for example. The bandgap of KBBF is 8.0 eV (the UV cutoff edge is about 155 nm).  During the calculation, the unit-cell parameters and atomic coordinates were obtained from XRD, and the RMT were set as K (2.50), Be(1.28), B(1.19), O(1.38)
> F(1.56). The core electron states were separated from the valence states by -8.0 Ry, and the Rkmax was set as 5.0. The Irreducible Brillouin Zon was sampled at 500 k-points without shifted meshes, and the convergent condition for SCF was set as 10E(-5). In
> order to get accurate GAP as described elsewhere, a mBJ method was used. While unlike many other successful example, the bandgap obtained is either larger or smaller than the experimental values. That is to say, when I chose ‘Original mBJ values (Tran,Blaha
> PRL102,226401)’to calculate, the GAP of KBBF is about 11.504 eV, much larger than the experimental values (8.0 eV), while when I chose ‘Unmodified BJ potential (Becke,Johnson J.Chem.Phys 124,221101’, the result is 7.301 eV, smaller than experimental values.
> Can anyone kindly tell me how to get accurate bandgap value of borates ?
> 
> PS: The KBBF.struct, KBBF.in1c, KBBF.in2c were added as attachment.
> 
> KBBF.struct
> 
> blebleble                                                                     
> R   LATTICE,NONEQUIV.ATOMS   5  155 R32                                       
> MODE OF CALC=RELA unit=bohr                                                   
>   8.364065  8.364065 35.454261 90.000000 90.000000120.000000                  
> ATOM  -1: X=0.00000000 Y=0.00000000 Z=0.00000000
>           MULT= 1          ISPLIT= 4
> K          NPT=  781  R0=.000050000 RMT= 2.50000     Z:  19.00000             
> LOCAL ROT MATRIX:    1.0000000 0.0000000 0.0000000
>                      0.0000000 1.0000000 0.0000000
>                      0.0000000 0.0000000 1.0000000
> ATOM  -2: X=0.72172000 Y=0.72172000 Z=0.72172000
>           MULT= 2          ISPLIT= 4
>       -2: X=0.27828000 Y=0.27828000 Z=0.27828000
> F          NPT=  781  R0=.000100000 RMT= 1.56        Z:   9.00000             
> LOCAL ROT MATRIX:    1.0000000 0.0000000 0.0000000
>                      0.0000000 1.0000000 0.0000000
>                      0.0000000 0.0000000 1.0000000
> ATOM  -3: X=0.80242000 Y=0.80242000 Z=0.80242000
>           MULT= 2          ISPLIT= 4
>       -3: X=0.19758000 Y=0.19758000 Z=0.19758000
> Be         NPT=  781  R0=.000100000 RMT= 1.28        Z:   4.00000             
> LOCAL ROT MATRIX:    1.0000000 0.0000000 0.0000000
>                      0.0000000 1.0000000 0.0000000
>                      0.0000000 0.0000000 1.0000000
> ATOM  -4: X=0.50000000 Y=0.19045000 Z=0.80955000
>           MULT= 3          ISPLIT= 8
>       -4: X=0.80955000 Y=0.50000000 Z=0.19045000
>       -4: X=0.19045000 Y=0.80955000 Z=0.50000000
> O          NPT=  781  R0=.000100000 RMT= 1.38        Z:   8.00000             
> LOCAL ROT MATRIX:    0.0000000 0.5000000 0.8660254
>                      0.0000000-0.8660254 0.5000000
>                      1.0000000 0.0000000 0.0000000
> ATOM  -5: X=0.50000000 Y=0.50000000 Z=0.50000000
>           MULT= 1          ISPLIT= 4
> B          NPT=  781  R0=.000100000 RMT= 1.19        Z:   5.00000             
> LOCAL ROT MATRIX:    1.0000000 0.0000000 0.0000000
>                      0.0000000 1.0000000 0.0000000
>                      0.0000000 0.0000000 1.0000000
>    6      NUMBER OF SYMMETRY OPERATIONS
> -1 0 0 0.00000000
>  0 0-1 0.00000000
>  0-1 0 0.00000000
>        1
>  0-1 0 0.00000000
> -1 0 0 0.00000000
>  0 0-1 0.00000000
>        2
>  0 0-1 0.00000000
>  0-1 0 0.00000000
> -1 0 0 0.00000000
>        3
>  0 1 0 0.00000000
>  0 0 1 0.00000000
>  1 0 0 0.00000000
>        4
>  0 0 1 0.00000000
>  1 0 0 0.00000000
>  0 1 0 0.00000000
>        5
>  1 0 0 0.00000000
>  0 1 0 0.00000000
>  0 0 1 0.00000000
>        6
> 
> KBBF.in1c
> 
> WFFIL  EF=-.100583812400   (WFFIL, WFPRI, ENFIL, SUPWF)
>   5.00       10    4 (R-MT*K-MAX; MAX L IN WF, V-NMT
>   0.30    4  0      (GLOBAL E-PARAMETER WITH n OTHER CHOICES, global APW/LAPW)
>  0   -2.30      0.002 CONT 1
>  0    0.30      0.000 CONT 1
>  1   -1.08      0.002 CONT 1
>  1    0.30      0.000 CONT 1
>   0.30    3  0      (GLOBAL E-PARAMETER WITH n OTHER CHOICES, global APW/LAPW)
>  0   -1.90      0.002 CONT 1
>  0    0.30      0.000 CONT 1
>  1    0.30      0.000 CONT 1
>   0.30    2  0      (GLOBAL E-PARAMETER WITH n OTHER CHOICES, global APW/LAPW)
>  0    0.30      0.000 CONT 1
>  0   -7.51      0.001 STOP 1
>   0.30    3  0      (GLOBAL E-PARAMETER WITH n OTHER CHOICES, global APW/LAPW)
>  0   -1.46      0.002 CONT 1
>  0    0.30      0.000 CONT 1
>  1    0.30      0.000 CONT 1
>   0.30    2  0      (GLOBAL E-PARAMETER WITH n OTHER CHOICES, global APW/LAPW)
>  0    0.30      0.000 CONT 1
>  1    0.30      0.000 CONT 1
> K-VECTORS FROM UNIT:4  -11.0       1.5   54   emin / de (emax=Ef+de) / nband
> 
> KBBF.in2c
> 
> TOT             (TOT,FOR,QTL,EFG,FERMI)
>   -14.00   52.00   0.50 0.05  1   EMIN, NE, ESEPERMIN, ESEPER0, iqtlsave
> TETRA    0.000      (GAUSS,ROOT,TEMP,TETRA,ALL      eval)
>   0 0  2 0 -3 3  4 0  4 3 -5 3  6 0  6 3  6 6
>   0 0  1 0  2 0  3 0  3 3 -3 3  4 0  4 3 -4 3  5 0  5 3 -5 3  6 0  6 3 -6 3  6 6 -6 6
>   0 0  1 0  2 0  3 0  3 3 -3 3  4 0  4 3 -4 3  5 0  5 3 -5 3  6 0  6 3 -6 3  6 6 -6 6
>   0 0  1 0  2 0  2 2 -2 2  3 0  3 2 -3 2  4 0  4 2 -4 2  4 4 -4 4  5 0  5 2 -5 2  5 4 -5 4  6 0  6 2 -6 2  6 4 -6 4  6 6 -6 6
>   0 0  2 0 -3 3  4 0  4 3 -5 3  6 0  6 3  6 6
>  14.00          GMAX
> NOFILE        FILE/NOFILE  write recprlist
> 
> 2, In some papers, they said ‘The potential and charge density in the muffin-tin (MT) spheres are expanded in spherical harmonics with lmax = 8 and non-spherical components up to lmax = 6.’I don’t know how to set different lmax value during the calculation.
> Can anyone tell me how to do ?
> 
> Thanks very much.
> 
> Yours
> 
> Qun Jing
> 
>  
> 
> 
>


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