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[Hua Bao <hbao@purdue.edu>]

Dear Abinit-user,

I am trying to do a CdTe band structure calculation using ABINIT. I  
followed the literature Physica B 373 (2006) 124-130. They used "  
first-principles pseudopotential method within the density functional  
formalism and the local density approximation using the Coperley- 
Alder functional for exchange-correlation energy, and standard norm- 
conserving pseudopotential of Troullier-Martins in non-relativistic  
form". Also, they use a mesh cutoff of 100 Ry and 108 k points. They  
are using a different codes.

Follow them, I calculated the band structure of CdTe with the similar  
parameters. However, I got a huge underestimate of band gap. The  
literature gives 1.88 eV, I got only 0.45 eV in the ABINIT  
calculation, experimental result is 1.56 eV. I even tried GW method.  
It still got 0.97 eV which is still much less than experimental  
result (some others using GW got 1.88 eV).

My question is how does this happen. Is band structure result codes- 
dependent? Is there anyway to improve the result for band structure?

BTW, I am using 48cd.pspnc and 52te.pspnc from the ABINIT website.  
Here is the input file for band structure calculation.
#Data set
ndtset 2

#Definition of the unit cell
acell  6.480 6.480 6.480  angstrom
rprim 0 .5 .5
      .5 0 .5
      .5 .5 0
#Definition of the atom types
ntypat 2
znucl 48 52

#coordinates
xred 0 0 0
     0.25 0.25 0.25
#Definition of the atoms
natom 2
typat 1 2

ecut 50.0         # Maximal kinetic energy cut-off, in Hartree
#Functional


#Data 1
#Definition of the k-point grid
ngkpt1 6 6 6
kptopt 1
prtden1 1
toldfe1 1.0d-6
nshiftk1 4
shiftk1  0.5 0.5 0.5  # These shifts will be the same for all grids
         0.5 0.0 0.0
         0.0 0.5 0.0
         0.0 0.0 0.5

#Dataset 2
iscf2 -2
getden2 -1
kptopt2 -3
nband2  18
prtwf2 0
prteig2 1
ndivk2 20 20 20
kptbounds2      0.5  0.0  0.0 # L point
                0.0  0.0  0.0 # Gamma point
                0.0  0.5  0.5 # X point
                1.0  1.0  1.0 # Gamma point in another cell
tolwfr2 1.0d-12
enunit2 1

#Definition of the SCF procedure
nstep 100          # Maximal number of SCF cycles
ixc 2  (I also tried 1).



Hua Bao
Graduate Research Assistant
School of Mechanical Engineering,
Purdue University
O: 765-494-6944