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[ธนูสิทธิ์ บุรินทร์ประโคน <thanusit@kku.ac.th>]

Dear Yang Ming

Just like Rossee suggested earlier if you want to calculate the GW
correction of 
X(0.0, 0.5,05) point,  this k point should be one of the k point list in
the KSS file.  

From your input file and the error messege,  it is obvious that the
k-point list in the KSS file doesn't contain the X-point. You can check
this out by looking  through the list following the kpt2 parameter in
you output file. Then, you may select one of the k-points from the list
for "kptgw4", instead of the X-point, just to see if the calculation can
be completed.

To get the X-point in the k-point list in the KSS file, in dataset2
calculation you need to add a few more parameters for generating k-point
grid  that contains the X-point.  The following example might do the job:
-----------------------------------------
# Dataset2: calculation of kss file
# Definition of k-points
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         # Option needed for Gamma
----------------------------------------------
The k-points (kpt2) generated by the above input parameters will contain
19 k-points including (0.5, 0.5, 0)  which, to the best of my knowledge,
is equivalent to the X-point (0, 0.5, 0.5) for fcc structure. Assign
"0.5, 0.5, 0" for "kptgw4" shoud give us the GW correction at the X point.

Also, set nbandkss2 to 200 can save some computing time and avoid
crashing caused by running out of memory. The "nbandkss" needed depends
on the "nband" to be used in the screening and GW calculations. In your
case, the nband for the two calculations are  25 and 100, respectively.
The nbandkss of 200 is enough for this job.


Hope this helps.

Kind regards, 
Thanusit Burinprakhon


> On February 16, 2008 10:39:38 PM ICT, mingyang@nus.edu.sg wrote:
> 
> Dear All,
> 
> I am a new one of ABINIT. I tried to get GW correction of Si band gap
at X point, but encoutered a problem. Might any one there give me a hand?
> 
> The error reported in log file is following:
>  
>  sigma : using b1gw and b2gw =            4           5
> 
>  findk : check if the k-points for sigma are in the set of BZ
> 
>  findk : ERROR -
>  k-point  0.000  0.500  0.500  not in the set of kbz
> 
>  leave_new : decision taken to exit ...
> __________________
> 
> And, the following is my input file:
> 
> # Crystalline silicon
> # Calculation of the GW correction to the direct band gap in Gamma
> # Dataset 1: ground state calculation
> # Dataset 2: calculation of the kss file
> # Dataset 3: calculation of the screening (epsilon^-1 matrix for W)
> # Dataset 4: calculation of the Self-Energy matrix elements (GW
corrections)
> 
> ndtset      4
> 
> kptopt   1            # Option for the automatic generation of k points
> ngkpt    4 4 4        # Density of k points
> 
> # Dataset1: usual self-consistent ground-state calculation
> # Definition of the k-point grid
> nkpt1    10
> nshiftk1  4
> shiftk1  0.5 0.5 0.5  # This grid is the most economical
>          0.5 0.0 0.0
>          0.0 0.5 0.0
>          0.0 0.0 0.5
> prtden1  1         # Print out density
> 
> 
> # Dataset2: calculation of kss file
> # Definition of k-points
> nbandkss2 -1
> npwkss2 0
> iscf2    -2             # Non self-consistent calculation
> getden2  -1             # Read previous density file
> # Dataset3: Calculation of the screening (epsilon^-1 matrix)
> optdriver3  3        # Screening calculation
> getkss3     -1       # Obtain KSS file from previous dataset
> nband3      25       # Bands to be used in the screening calculation
> ecutwfn3    3.6      # Planewaves to be used to represent the
wavefunctions
> ecuteps3    6.0      # Dimension of the screening matrix
> ppmfrq3    16.7 eV  # Imaginary frequency where to calculate the screening
> 
> # Dataset4: Calculation of the Self-Energy matrix elements (GW
corrections)
> optdriver4  4        # Self-Energy calculation
> getkss4     -2       # Obtain KSS file from dataset 1
> getscr4     -1       # Obtain SCR file from previous dataset
> nband4      100      # Bands to be used in the Self-Energy calculation
> ecutwfn4    5.0      # Planewaves to be used to represent the
wavefunctions
> ecutsigx4    6.0      # Dimension of the G sum in Sigma_x
>                      # (the dimension in Sigma_c is controlled by npweps)
> nkptgw4      1                # number of k-point where to calculate
the GW correction
> kptgw4                       # k-points
>   0.000    0.500  0.500    # (X)
> bdgw4       4  5             # calculate GW corrections for bands from
4 to 5
> 
> 
> # Definition of the unit cell: fcc
> acell  3*10.217        # This is equivalent to   10.217 10.217 10.217
> rprim  0.0  0.5  0.5   # FCC primitive vectors (to be scaled by acell)
>        0.5  0.0  0.5
>        0.5  0.5  0.0
> 
> # Definition of the atom types
> ntypat  1         # There is only one type of atom
> znucl 14          # The keyword "znucl" refers to the atomic number of the
>                   # possible type(s) of atom. The pseudopotential(s)
>                   # mentioned in the "files" file must correspond
>                   # to the type(s) of atom. Here, the only type is
Silicon.
> 
> # Definition of the atoms
> natom 2           # There are two atoms
> typat  1 1        # They both are of type 1, that is, Silicon.
> xred              # Reduced coordinate of atoms
>       0.0  0.0  0.0
>       0.25 0.25 0.25
> 
> # Definition of the planewave basis set (at convergence 16 Rydberg 8
Hartree)
> ecut 8.0          # Maximal kinetic energy cut-off, in Hartree
> 
> # Use only symmorphic operations
> symmorphi 0
> 
> # Definition of the SCF procedure
> nstep   10        # Maximal number of SCF cycles
> diemac  12.0      # Although this is not mandatory, it is worth to
>                   # precondition the SCF cycle. The model dielectric
>                   # function used as the standard preconditioner
>                   # is described in the "dielng" input variable section.
>                   # Here, we follow the prescription for bulk silicon.
> tolwfr  1.0d-10
> 
> # This line added when defaults were changed (v5.3) to keep the
previous, old behaviour
>   iscf 5
> 
> ____________
> 
> Thanks.
> 
> Best regards,
> Yang Ming