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[Michael Bachmann <Michael.Bachmann@exp1.physik.uni-giessen.de>]

Yousong Gu (顾有松) schrieb:
> Hi, every one,
> I tried to calculate the GWA correction to the band gap of wurtzite
> ZnO, it fails at the start of second stage. From the error massage,it
> seems something wrong with K point handling. I tried to calculate the
> zinc blende ZnO, it passed. Please help me find what's wrong. Are
> there any special treatments required for hexagonal system?
> My input files is as follow:
> **************************************************************************
> ndtset 3
>
> nbandkss1 -1
> nband1 50
>
> optdriver2 3
> getkss2 -1
> nband2 80
> ecutwfn2 10.0
> ecuteps2 12.0
> ppmfrq2 16.7 eV
> awtr2 0
>
> optdriver3 4
> getkss -2
> getscr -1
> nband3 160
> ecutwfn3 15.0
> ecutsigx3 18.0
> nkptgw3 1
> kptgw3 0.0833333333333 0.08333333333333 0.125
> bdgw3 26 27
>
> #system descriptions
> acell 6.2704613542E+00 6.2704613542E+00 1.0074985298E+01
> angdeg 90 90 120
>
> ntypat 2
> znucl 30 8
>
> natom 4
> typat 1 1 2 2
>
> xred
> 0.3333333333333333 0.666666666666667 0.00
> 0.6666666666666667 0.333333333333333 0.50
> 0.3333333333333333 0.666666666666667 0.38031837152
> 0.6666666666666667 0.333333333333333 0.88031837152
>
> #Kpoint setup
> nkpt 42
> kptopt 1
> ngkpt 6 6 4
> nshiftk 1
> shiftk 0.5 0.5 0.5
>
> #electronic
> #iscf 17
> #ixc 11
> ecut 15
> pawecutdg 30
> nstep 40
> toldfe 1.0d-6
>
> #Common
> diemac 12.0
> istwfk 42*1
> symmorphi 0
>
> nsym 0
> optforces 2 optstress 1
> kssform 3
> ****************************************************************************
> Here is the error message:
> together with 6 symmetry operations and time-reversal
> yields 576 points in the Brillouin Zone (BZ) :
>
>
>
> m_bz_mesh.F90:1685:ERROR
> Not able to found umklapp G0 vector among ***** vectors
> Increase mg0sh such as k1-k2 = kf+G0, present value = 25
> point1 = 3 -1.66666667E-01 8.33333333E-02 1.25000000E-01
> point2 = 2 -1.66666667E-01 8.33333333E-02 0.00000000E+00
>
> *********************************************************************
> Thans in advance.
> Yousong Gu
> Department of Material Physics
> University of Sci. & Tech. Beijing
this problem occured to me 2 month ago. Here is my discription of the
problem again. i haven't found a solution yet!

Hi, i have a Problem with a GW calculation. I want to calculate the Bandgab
correction for Zno/Wurzite structure at the Gammapoint. Therefor I simply took
the input card from the first GW tutorial and .replaced the geometry data. the
following Error occurred by running this Input Card 

"not able to found umklapp G0 vector among vectors',
 Increase mg0sh such as k1-k2 = kf+G0, present value = 25"

because oft this error i changed the source code and raised mg0sh until the
error did not occured. To prevent this error mg0sh has to be about 525. Now my
Job needs about 25gbyte ram and takes very long and the  results are nonsense
in the way that my Bandgab decreases. Another Problem that occurred is that 
the
numbers of electrons in my unit cell should by 36 but nelect has the value
35,555.
Has anybody an idee what's wrong here? 
Anyway thanks for reading this so far.

Here are my input card

# Crystalline ZN0
# 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    10 10 8        # Density of k points

# Dataset1: usual self-consistent ground-state calculation
# Definition of the k-point grid
nkpt1    0
nshiftk1  1
shiftk1  0.0 0.0 0.5  # This grid is the most economical
         
prtden1  1         # Print out density

# Dataset2: calculation of kss file
# Definition of k-points
nkpt2    0             # A set of 19 k-points containing Gamma
nshiftk2  1
shiftk2  0.0 0.0 0.0  # This grid contains the Gamma point
         
istwfk2  1000*1                    # Option needed for Gamma
iscf2    -2             # Non self-consistent calculation
getden2  -1             # Read previous density file
nband2   50
nbandkss2 300        # Number of bands to store in KSS file

# Dataset3: Calculation of the screening (epsilon-1 matrix)
optdriver3  3        # Screening calculation
getkss3     -1       # Obtain KSS file from previous dataset
nband3      300       # Bands to be used in the screening calculation
ecutwfn3    15      # Planewaves to be used to represent the wavefunctions
ecuteps3    15      # 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      300      # Bands to be used in the Self-Energy calculation
ecutwfn4    15.0      # Planewaves to be used to represent the wavefunctions
ecutsigx4    15.0      # 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    0.000    0.000    # (Gamma)
bdgw4       18  19             # calculate GW corrections for bands from 18 to
19


#Definition of the unit cell


acell 3.23 3.23 5.168 angstrom
 

rprim 0.5 -0.86602540378  0.0  
      0.5 0.86602540378  0.0 
      0.0  0.0  1.0
       
       
#Definition of the atom types
ntypat 2          # There is only one type of atom
znucl  30 8         # 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 Aluminum
                         

#Definition of the atoms
natom 4           # 2 C-Atome pro Layer
typat 1 1 2 2     # Alle 2ZN und 2 O -Atome
xred              # This keyword indicate that the location of the atoms
                  # will follow, one triplet of number for each atom
                  
   1/3  2/3  0.0     # ZN Atome aus erster Schicht
   2/3  1/3  0.5     # ZN Atome mitte der Zelle
   
   1/3 2/3 0.381    #Atome aus zweiter Schicht
   2/3 1/3 0.881     


# Definition of the planewave basis set (at convergence 16 Rydberg 8 Hartree)
ecut 25.0          # Maximal kinetic energy cut-off, in Hartree

# Use only symmorphic operations
symmorphi 0

# Definition of the SCF procedure
nstep   20        # 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