Dear Lyudmila and BHamu Thank you for your suggestions. I have already used 18*18*3 for supercell and 18*18*18, but found difference in plasma frequency for supercell and bulk. Should plasma frequency be same for bulk and supercell? or I should use the new plasma frequency obtained from super cell calculation?
@Lyudmila | In terms of accuracy, this is the worst. but why? On Tue, Oct 13, 2015 at 10:55 AM, Dr. K. C. Bhamu <kcbham...@gmail.com> wrote: > > > Dear sajjad > > I am also a beginner but I must suggest you to choose 18*18*3 k points for > 1*1*6 supercell in comparison with bulk. > As volume in real space is inversely proportional to volume of reciprocal > space. Larger the volume in real space lower the volume in reciprocal > space. So while computing properties of 1*1*6 structure you are minimizing > your volume in z direction and hence need less k-points. > > I appreciate any comment on this from DFT experts. > > > Sincerely > Bhamu > > I have computed PF for bulk Na and its value is *5.943 eV* with k-mesh >> *18*18*18*. >> >> Then I constructed a supercell 1*1*6 >> > > ...>>>>>>> use 18*18*3 k points for 1*1*6 supercell. > > and run the calculation with different k-meshes and obtained PF values. >> The details are >> >> *K-mesh PF (x/z components in eV)* >> >> *24*24*24 5.7097 / 5.8192* >> >> >> *36*36*24 5.7614 / 5.8098 * >> >> >> *50*50*10 5.9358 / 5.6280 * >> >> *50*50*30 5.9365 / 5.8079* >> >> My question is why PF is very sensitive to k-mesh selection? and which >> value of PF is required for correct dielectric constant calculation? Do I >> need *PF = 5.943 eV* for the supercell and then, definitely, need more >> test calculation for right k-mesh selection? >> >> -- >> Kind Regards >> Muhammad Sajjad >> Post Doctoral Fellow >> KAUST, KSA. >> >> _______________________________________________ >> Wien mailing list >> Wien@zeus.theochem.tuwien.ac.at >> http://zeus.theochem.tuwien.ac.at/mailman/listinfo/wien >> SEARCH the MAILING-LIST at: >> http://email@example.com/index.html >> >> > > _______________________________________________ > Wien mailing list > Wien@zeus.theochem.tuwien.ac.at > http://zeus.theochem.tuwien.ac.at/mailman/listinfo/wien > SEARCH the MAILING-LIST at: > http://firstname.lastname@example.org/index.html > > -- Kind Regards Muhammad Sajjad Post Doctoral Fellow KAUST, KSA.
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