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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