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[thanusit@kku.ac.th]

Dear Zhang

I have tried the GW calculation to determine the diamond band gap at Gamma. 
By carefully following the convergence test series in tutorial lesson GW1, I 
came up with the input file listed below. The caluculated diamond gap at 
Gamma was 7.428 ev (see below) which is very close the to the the 
experimental value of 7.5 eV. Not too bad! I think.

The job was run unsing paralleised Abinit 5.4.3, with mpi. The platform was 
scientific linux 5.0 on intel Core 2 Quad Q6600, 2.4GHz. The job took around 
40 minutes to finish.

Hope this help.

Best regards,
Thanusit Burinprakhon

Input file:
---------------------------
ndtset 4          

kptopt   1             
ngkpt    4 4 4         

#Dataset 1 : usual self-consistent calculation for ground state charge density

kptopt1 1          
nshiftk1 4
shiftk1  0.5 0.5 0.5    
         0.5 0.0 0.0
         0.0 0.5 0.0
         0.0 0.0 0.5
prtden1  1         

# Dataset2: calculation of KSS file
nkpt2    19             # A set of 19 k-points containing Gamma
nshiftk2  4
shiftk2  0.0 0.0 0.0    # This grid contains the Gamma point
         0.0 0.5 0.5
         0.5 0.0 0.5
         0.5 0.5 0.0
istwfk2  19*1         
iscf2    -2           
getden2  -1          
nband2   10           
nbandkss2 200        

# Dataset3: Calculation of the screening (epsilon^-1 matrix)
optdriver3   3       
getkss3     -1      
nband3      150      # Optimum value from convergence study
ecutwfn3    15       # Optimum value from convergence study
ecuteps3    20       # Optimum value from convergence study
ppmfrq3    16.7 eV   

# Dataset4: Calculation of the Self-Energy matrix elements (GW corrections)

optdriver4    4        
getkss4      -2        
getscr4      -1        
nband4        150      # Optimum value from convergence study
ecutwfn4      30       # Optimum value from convergence study
ecutsigx4     26       # Optimum value from convergence study

nkptgw   1              
kptgw    0.0 0.0 0.0     
bdgw     4  5           

# Definition of the unit cell: fcc
acell  3*6.693         # Coverged lattice parameters with LDA
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  1         
znucl   6         

# Definition of the atoms
natom 2          
typat 1 1        
xred             
     0.0 0.0 0.0
     1/4 1/4 1/4

# Definition of the planewave basis set (at convergence 16 Rydberg 8 Hartree)
ecut 40.0         # Optimum value for the convergence of total energy

# Definition of the SCF procedure
nstep   100       
diemac  12.0      
tolwfr  1.0d-10   

nsym 0
symmorphi 0     
iscf 5
ixc  1
-----------------------------
 GW results:

 Perturbative Calculation

 k =    0.000   0.000   0.000
 Band     E0 <VxcLDA>   SigX SigC(E0)      Z dSigC/dE  Sig(E)    E-E0       E
    4  12.820 -16.911 -18.986   1.301   0.827  -0.209 -17.551  -0.641  12.179
    5  18.450 -15.681  -9.567  -4.718   0.829  -0.206 -14.524   1.157  19.607

 E^0_gap          5.630
 E^GW_gap         7.428 <<<<<<
 DeltaE^GW_gap    1.797
--------------------------------