<div dir="ltr">Dear Professor Blah<div>Thank you for your quick response. Yes I found that completely converged (with the best k-mesh) leads to the same results on changing k-meshes for optical properties. Na is better in k-mesh selection than that of Al. </div><div><br></div><div>Actually I am expanding structure in z-direction. In my opinion, I must consider both w_p_xx and w_p_zz, as former is changing slowly while an abrupt change is found in the later component of PF. Am I right?</div><div>Simply, except cubic system, both tensor components of PF must take in account?</div><div>True Regards </div></div><div class="gmail_extra"><br><div class="gmail_quote">On Fri, Oct 30, 2015 at 9:28 AM, 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">
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.<br>
<br>
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. <br>
<br>
PS: I know that for Al one needs MANY more k-points to get a
converged value. No idea about Na.<div><div class="h5"><br>
<br>
<div>Am 29.10.2015 um 21:50 schrieb Muhammad
Sajjad:<br>
</div>
<blockquote type="cite">
<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><br>
<br>
<br>
<br>
<div>Am 29.10.2015 um 10:35 schrieb Muhammad Sajjad:<br>
</div>
</div>
</div>
<blockquote type="cite">
<div>
<div>
<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"></a><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>
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<div>Kind Regards</div>
<div>Muhammad Sajjad </div>
<div>Post Doctoral Fellow</div>
<div>KAUST, KSA.</div>
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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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