Automatic k-point generation
Posted: Fri Feb 01, 2019 8:18 am
Dear all,
I am new to Abinit and just try to perform some GS-calculations for different systems, but get stuck with k-point grid symmetry.
Suppose I'm taking the AlAs system from the RF2 tutorial. When I run the code with the following option
everything is OK, but when I try to remove the shifting options, i.e. leave just
the code complains that
I don't quite get this as e.g. in Elk code we have a similar parameter ngridk, which can be set to any value without need to set the shifts (or may be Elk does it automatically?). In other words, what should I do in a general case if I have some structure and I don't know how to set the shift options correctly and I just want to control the number of grid points for K points generation? Can Abinit solve out these symmetry issues automatically?
Thank you in advance,
Anton F.
I am new to Abinit and just try to perform some GS-calculations for different systems, but get stuck with k-point grid symmetry.
Suppose I'm taking the AlAs system from the RF2 tutorial. When I run the code with the following option
Code: Select all
ngkpt 6 6 6
nshiftk 4 # Use one copy of grid only (default)
shiftk 0.0 0.0 0.5 # This gives the usual fcc Monkhorst-Pack grid
0.0 0.5 0.0
0.5 0.0 0.0
0.5 0.5 0.5
everything is OK, but when I try to remove the shifting options, i.e. leave just
Code: Select all
ngkpt 6 6 6
the code complains that
Code: Select all
Chksymbreak=1 . It has been observed that the k point grid is not symmetric :
for the symmetry number 2
with symrec= 0 0 1 -1 -1 -1 1 0 0
the symmetric of the k point number 512 with components -6.250000E-02 -6.250000E-02 -6.250000E-02
does not belong to the k point grid.
Read the description of the input variable chksymbreak,
You might switch it to zero, or change your k point grid to one that is symmetric.
I don't quite get this as e.g. in Elk code we have a similar parameter ngridk, which can be set to any value without need to set the shifts (or may be Elk does it automatically?). In other words, what should I do in a general case if I have some structure and I don't know how to set the shift options correctly and I just want to control the number of grid points for K points generation? Can Abinit solve out these symmetry issues automatically?
Thank you in advance,
Anton F.