There is definitely no need to go to such a high number of k-points.
In the paper of Claudia, they were looking at metallic compounds, for
which we need to have a very dense k-mesh (for the intraband transitions).
In your case you expect a semiconductor and thus you will have only
interband transitions. Thus 6000 kpoints is already converged to my
point of view.
I should say that the best way to insure the convergency in the present
case is to plot the epsilon2 as a function of the energy for instance
and to compare this quantity with different k-meshes. In your case, try
to do 300 kpoints first and then 500, 1000, 2000, 3000 kpoints ... You
will certainly reach the convergency at about 1000-2000 kpoints ...
Regards
Xavier
P.S.: The values obtained for 90000 kpoints are curious but I imagine
that you had a prob
Le 9/30/2013 4:59 PM, ali ghafari a écrit :
Dear Prof. Blaha
I have calculated the optical properties of TiSe2 by MBJ potential
with 6000, 50000 and 90000 kpoints which generated after scf by x kgen
as discussed in the UG.
As discussed in the paper of Prof. Claudia Draxl (computer physics
comm. 175, 1-14 (2006)) the sum rule 1 and 2 show 'an effective number
of electrons contributing to the absoption process as a function of
energy'.
but my calculations lead to :
6000 kpoints:
sum rule 1: Int(sigma)dw 19.14
sum rule 2: Int(eloss.w)dw 18.93
sum rule 3: Int(eloss/w)dw 1.51
50000 kpoints
sum rule 1: Int(sigma)dw 19.08
sum rule 2: Int(eloss.w)dw 18.94
sum rule 3: Int(eloss/w)dw 1.52
90000 kpoints
sum rule 1: Int(sigma)dw 10.125
sum rule 2: Int(eloss.w)dw 10.035
sum rule 3: Int(eloss/w)dw 1.51
the results show that in 90000 kpoints the value of 'sum rule 2'
significantly decreases . in the UG it has mensioned that for the
optic we need dense kpoints but how many? how can I check it for optic?
Best Regards
Ali
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