`Usually, different properties require different k-meshes. So it should`

`be ok to converge the scf with a smaller k-mesh (it still must be a`

`"good" one), but use more k-points for a plot of the DOS or optics.`

`Please repeat the optics calculation with a series of k-meshes and plot`

`w_p as funktion of the k-mesh. You should find out in this way the`

`converged value.`

`PS: I know that for Al one needs MANY more k-points to get a converged`

`value. No idea about Na.`

Am 29.10.2015 um 21:50 schrieb Muhammad Sajjad:

Dear Prof. P BlahaThank you very much for yous fruitful suggestions. However, I did notchange RKmax. For cubic Na only W_p_xx is enough but after makingsupercell (1 1 6) still I need only w_p_xx and forget about w_p_zz,though the system is tetragonal now. Is it right I understood?Second thing is it principally right that one converges SCF withsmall k-mesh say 30*30*5 and then use the same scf ao get OPTICALproperties with k-mesh say 90*90*15? I mean no need to converge scfwith 90*90*15.Kind RegardsOn Thu, Oct 29, 2015 at 9:03 PM, Peter Blaha<pbl...@theochem.tuwien.ac.at <mailto:pbl...@theochem.tuwien.ac.at>>wrote:In principle you are doing thinks now correct. In reality, however, we use the tetrahedra-method in the integration of the BZ to calculate a joint-density-of-states. And for a metal !!! here there is a difference between k-meshes in the small or large cell. (it is related to the "back-folding" problem and in the supercell there are less tetrahedra and thus less possibilities to interpolate for the tetrahedron method than in the small cell). In any case, you need to consider two things: a) You have to decide to which accurcy a certain number should be calculated. Typically, a plasma frequency would be quoted with one or two digits after the comma (i.e. 5.9 or at most 5.94 eV). b) Then you have to converge the numbers with respect to k-mesh (but also Rkmax !!) Definitely you should use a ratio of 6:1 for the supercell, but eventually you need to increase the mesh until there are no changes within the desired accuracy. In your case, 90x15 is almost sufficient, but not quite if you want two digits accuracy. c) in a cubic system, of course it is useless to quote two tensor components and one is sufficient. Am 29.10.2015 um 10:35 schrieb Muhammad Sajjad:Dear Prof. Blaha I did some calculation for Bulk Na (bcc, space gp #229_Im-3m) wiht k-mesh 30*30*30 and found the plasma frequency (in case.outputjoint) as Plasma frequencies: w_p_xx w_p_zz [eV] 5.9446 5.9446 Now I constructed a supercell 1*1*6 (definitely symmetry reduced and now sp.gp <http://sp.gp> is 1_P1), used k-mesh 30*30*5 and found Plasma frequencies (much deviating from bulk values): w_p_xx w_p_zz [eV] 5.76146 5.3446 Then used k-mesh 90*90*15 and found Plasma frequencies (w_p_zz is deviating from bulk w_p_zz ): w_p_xx w_p_zz [eV] 5.9485 5.8903 I have read the previous post (https://www.mail-archive.com/wien@zeus.theochem.tuwien.ac.at/msg09782.html) but it is not speaking about w_p_zz. So when I plot epsilon data for w_p_xx then it is matching with that of bulk but when I use w_p_zz then it is definitely away from bulk. Should I consider w_p_zz or use "number of choice = 1 in case.inop" and plot epsilon only with w_p_xx ? Kind Regards Muhammad Sajjad Post Doctoral Fellow KAUST, KSA. _______________________________________________ Wien mailing list Wien@zeus.theochem.tuwien.ac.at <mailto:Wien@zeus.theochem.tuwien.ac.at> http://zeus.theochem.tuwien.ac.at/mailman/listinfo/wien SEARCH the MAILING-LIST at:http://www.mail-archive.com/wien@zeus.theochem.tuwien.ac.at/index.html_______________________________________________ Wien mailing list Wien@zeus.theochem.tuwien.ac.at <mailto:Wien@zeus.theochem.tuwien.ac.at> http://zeus.theochem.tuwien.ac.at/mailman/listinfo/wien SEARCH the MAILING-LIST at: http://www.mail-archive.com/wien@zeus.theochem.tuwien.ac.at/index.html -- 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://www.mail-archive.com/wien@zeus.theochem.tuwien.ac.at/index.html

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