Problem in screening calculation

[lvjian8596]

Dear all,
I do a GW calculation. There is a error about the screening calculation as follows:

m_bz_mesh.F90:1683:ERROR
Not able to found umklapp G0 vector among ***** vectors
Increase mg0sh such as k1-k2 = kf+G0, present value = 25
point1 = 1 0.00000000E+00 0.00000000E+00 1.00000000E-01
point2 = 2 0.00000000E+00 0.00000000E+00 -2.00000000E-01

-P-0000
-P-0000 leave_new : decision taken to exit ...

It would be very nice if someone could give me some suggestion. Thank you in advance.


The input file is :

# Dataset 1: ground state calculation and of the kss file
# Dataset 2: calculation of the screening (epsilon^-1 matrix for W)
# Dataset 3: calculation of the Self-Energy matrix elements (GW corrections)

ndtset 3
gwpara 2
nsym 0
# Definition of parameters for the calculation of the KSS file
kssform1 3
nbandkss1 -1 # Number of bands in KSS file (-1 means the maximum possible)
nband1 24 # Number of (occ and empty) bands to be computed
#istwfk1 *1

# Calculation of the screening (epsilon^-1 matrix)
optdriver2 3 # Screening calculation
getkss2 -1 # Obtain KSS file from previous dataset
nband2 24 # Bands to be used in the screening calculation
ecutwfn2 5 # Cut-off energy of the planewave set to represent the wavefunctions
ecuteps2 5 # Cut-off energy of the planewave set to represent the dielectric matrix
ppmfrq2 16.7 eV # Imaginary frequency where to calculate the screening
awtr2 0 # Note : the default awtr 1 is better

# Calculation of the Self-Energy matrix elements (GW corrections)
optdriver3 4 # Self-Energy calculation
getkss3 -2 # Obtain KSS file from dataset 1
getscr3 -1 # Obtain SCR file from previous dataset
nband3 50 # Bands to be used in the Self-Energy calculation
ecutwfn3 5 # Planewaves to be used to represent the wavefunctions
ecutsigx3 5 # Dimension of the G sum in Sigma_x
# (the dimension in Sigma_c is controlled by npweps)
nkptgw3 1 # number of k-point where to calculate the GW correction
kptgw3 # k-points
0.000 0.000 0.100
bdgw3 18 19 # calculate GW corrections for bands from 4 to 5

# Data common to the three different datasets
# Definition of the unit cell: fcc
acell 3*1.88972687777435527243
rprim 3.906850 2.159200 0.000000
-3.906850 2.159200 0.000000
0.000000 0.000000 4.306300

# Definition of the atom types
ntypat 1 # There is only one type of atom
znucl 3 # 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 12 # There are two atoms
typat 1 1 1 1 1 1 1 1 1 1 1 1 # They both are of type 1, that is, Silicon.
xred # Reduced coordinate of atoms
0.7248706507699936 0.0580392869466166 0.1563919616237470
0.7751293492300064 0.4419607130533834 0.6563919616237470
0.9419607130533834 0.2751293492300064 0.8436080383762530
0.5580392869466166 0.2248706507699936 0.3436080383762530
0.2751293492300064 0.9419607130533834 0.8436080383762530
0.2248706507699936 0.5580392869466166 0.3436080383762530
0.0580392869466166 0.7248706507699936 0.1563919616237470
0.4419607130533834 0.7751293492300064 0.6563919616237470
0.6738931128214887 0.6738931128214887 0.0619381903174769
0.8261068871785113 0.8261068871785113 0.5619381903174769
0.3261068871785113 0.3261068871785113 0.9380618096825231
0.1738931128214887 0.1738931128214887 0.4380618096825231


# Definition of the k-point grid
kptopt 1
ngkpt 4 4 4
nshiftk 1
shiftk 0.0 0.0 0.4 # These shifts will be the same for all grids
istwfk *1 # This is mandatory in all the GW steps.

# Use only symmorphic operations
symmorphi 0

# Definition of the planewave basis set (at convergence 16 Rydberg 8 Hartree)
ecut 10 # Maximal kinetic energy cut-off, in Hartree
pawecutdg 20
# Definition of the SCF procedure
nstep 20 # Maximal number of SCF cycles
toldfe 1.0d-8 # Will stop when this tolerance is achieved on total energy
#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.


# This line added when defaults were changed (v5.3) to keep the previous, old behaviour
iscf 17
#Definition of occupation numbers
occopt 6
tsmear 0.005

[bruneval]

Hi,

I think the kshift is not correct for the GW part. Try to use either 0. 0. 0.5 or 0. 0. 0. and let us know if it's working better.
Good luck.

Fabien

[lvjian8596]

Hi,

I think the kshift is not correct for the GW part. Try to use either 0. 0. 0.5 or 0. 0. 0. and let us know if it's working better.
Good luck.

Fabien

Dear Bruneval,
Thank you very much for you reply! If I use 0. 0. 0.5 or 0. 0. 0. , it workd well.
But I wanted to do a GW calculation at a common K-point 0.0 0.0 0.1, Could you
give me some advise about how can generate this point? The space group symmetry
is No 64. Cmca.

Thanks and Best regards,

[bruneval]

You may be able to calculate the GW corrections for your non convential grid by switching off the symmetries.
Set something like nsym=1
This comes with no warranty at all and the calculations are going to be much heavier.

I would rather try to find the specific k-point you want from a conventional set with a grid fine enough.
For instance the point 0. 0. 0.1 is going to be present in a shifted 5x5x5 grid. I guess...

Good luck

Fabien