<div dir="ltr">Dear Prof. P Blaha<div>Thank you very much for yous fruitful suggestions. However, I did not change RKmax. For cubic Na only W_p_xx is enough but after making supercell (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?</div><div>Second thing is it principally right that one converges SCF with small k-mesh say 30*30*5 and then use the same scf ao get OPTICAL properties with k-mesh say 90*90*15? I mean no need to converge scf with 90*90*15.</div><div> Kind Regards</div></div><div class="gmail_extra"><br><div class="gmail_quote">On Thu, Oct 29, 2015 at 9:03 PM, Peter Blaha <span dir="ltr"><<a href="mailto:pblaha@theochem.tuwien.ac.at" target="_blank">pblaha@theochem.tuwien.ac.at</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
<div text="#000000" bgcolor="#FFFFFF">
In principle you are doing thinks now correct. <br>
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).<br>
<br>
In any case, you need to consider two things:<br>
<br>
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).<br>
<br>
b) Then you have to converge the numbers with respect to k-mesh (but
also Rkmax !!)<br>
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.<br>
<br>
c) in a cubic system, of course it is useless to quote two tensor
components and one is sufficient.<div><div class="h5"><br>
<br>
<br>
<br>
<div>Am 29.10.2015 um 10:35 schrieb Muhammad
Sajjad:<br>
</div>
</div></div><blockquote type="cite"><div><div class="h5">
<div dir="ltr">Dear Prof. Blaha
<div><br>
</div>
<div>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</div>
<div> Plasma frequencies: </div>
<div><br>
</div>
<div> w_p_xx w_p_zz [eV]</div>
<div><br>
</div>
<div> 5.9446 5.9446 </div>
<div><br>
</div>
<div>Now I constructed a supercell 1*1*6 (definitely symmetry
reduced and now <a href="http://sp.gp" target="_blank">sp.gp</a>
is <font color="#0000ff">1_P1</font>), used k-mesh 30*30*5
and found<br clear="all">
<div>
<div>Plasma frequencies (<font color="#ff0000">much
deviating from bulk values</font>): </div>
<div><br>
</div>
<div> w_p_xx w_p_zz [eV]</div>
<div><br>
</div>
<div> 5.76146 5.3446 </div>
</div>
<div><br>
</div>
<div>Then used k-mesh 90*90*15 and found </div>
<div>
<div>Plasma frequencies (<font color="#ff0000">w_p_zz is
deviating from bulk w_p_zz </font>): </div>
<div><br>
</div>
<div> w_p_xx w_p_zz [eV]</div>
<div><br>
</div>
<div> 5.9485 5.8903 </div>
</div>
<div><br>
</div>
<div>I have read the previous post (<a href="https://www.mail-archive.com/wien@zeus.theochem.tuwien.ac.at/msg09782.html" target="_blank">https://www.mail-archive.com/wien@zeus.theochem.tuwien.ac.at/msg09782.html</a>)
but it is not speaking about <span style="color:rgb(255,0,0)">w_p_zz. </span><font color="#000000">So when I plot epsilon data for </font><font color="#0000ff">w_p_xx</font><span style="color:rgb(0,0,0)"> then it is matching with that of
bulk but when I use </span><span style="color:rgb(255,0,0)">w_p_zz</span><font color="#000000"> then </font><span style="color:rgb(0,0,0)">it is </span><span style="color:rgb(0,0,0)">definitely</span><span style="color:rgb(0,0,0)"> away from bulk. Should I
consider </span><span style="color:rgb(255,0,0)">w_p_zz</span><span style="color:rgb(0,0,0)"> or use "number of choice = 1 in
case.inop" and plot epsilon only with</span> <span style="color:rgb(0,0,255)">w_p_xx ?</span></div>
<div>
<div dir="ltr">
<div><br>
</div>
<div><br>
</div>
<div>Kind Regards</div>
<div>Muhammad Sajjad </div>
<div>Post Doctoral Fellow</div>
<div>KAUST, KSA.</div>
</div>
</div>
</div>
</div>
<br>
<fieldset></fieldset>
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<br></blockquote></div><br><br clear="all"><div><br></div>-- <br><div class="gmail_signature"><div dir="ltr"><div>Kind Regards</div><div>Muhammad Sajjad </div><div>Post Doctoral Fellow</div><div>KAUST, KSA.</div></div></div>
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