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["Peelaers Hartwin" <Hartwin.Peelaers@student.ua.ac.be>]

Title: Calculation bandmass in GaAs

Dear Abinitioners,


I'm trying to calculate the effective bandmass of GaAs. To do that I'm
fitting a 4th order polynomial expressing the energy as function of k around
the gamma point. (Before that I also rescaled the reduced coordinates of the
k-points using the values of the reciprocal unit vectors.) The effective
bandmass is then the reverse of two times the coefficient in front of k^2.
This procedure works well for Si (where I fitted the energy around the
minimum in the conduction band close to the X point), but not for GaAs,
where I obtain a value of 0.019 (0.021 when the odd powers of k are forced
to be zero). Earlier ab initio investigations (PRB 46, 2086(1992)) obtained
the correct value of 0.064.
Attached you will find my input file. This input file uses hgh
pseudopotentials (including 3d electrons). I also tried other
pseudopotentials with very similar results. To improve accuracy of the
outputted values I changed the abinit source files to output more digits.
Does anybody see what I am doing wrong? Can someone give a suggestion on how
to improve my results?

Best Regards,

Hartwin Peelaers



---------------------------------------------
University of Antwerp - Department of Physics
CMT - U208
Groenenborgerlaan 171
B-2020 Antwerp
Belgium



# Crystalline GaAs
#Set 1 : ground state self-consistency
ndtset 2
ecut   170
kptopt   1         
toldfe   1.0d-9     
prtden1 1
nband1 30
pspso 2 2
nspinor 2
prtvol 2

#Definition of the unit cell
    acell   3*10.61        
    rprim   0.0  0.5  0.5  
            0.5  0.0  0.5   
            0.5  0.5  0.0  

#Definition of the atom types
   ntypat   2        
    znucl   31 33    

#Definition of the atoms
    natom   2        
    typat   1 2      
                      
     xred   0.0  0.0  0.0
            0.25 0.25 0.25 
     
#Definition of the k-point grid

ngkpt  4 4 4 

nshiftk   4             
 shiftk   0.0 0.0 0.5   
          0.0 0.5 0.0
          0.5 0.0 0.0
          0.5 0.5 0.5

#Set 2
iscf2    -2
getden2  -1
kptopt2  -1
nband2   30
ndivk2   100
kptbounds2 0 -0.01 -0.01  #along delta-line
           0   0     0
tolwfr2  1.0d-12

#Definition of the SCF procedure
     iscf   5         
    nstep   25        
   diemac   9.0