<div dir="ltr">Dear Lyudmila and BHamu<div>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?</div><div><br></div><div>@Lyudmila </div><div>| In terms of accuracy, this is the worst.<br></div><div>but why?</div><div><br></div><div><br></div></div><div class="gmail_extra"><br><div class="gmail_quote">On Tue, Oct 13, 2015 at 10:55 AM, Dr. K. C. Bhamu <span dir="ltr"><<a href="mailto:kcbhamu85@gmail.com" target="_blank">kcbhamu85@gmail.com</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div dir="ltr"><div class="gmail_extra"><div class="gmail_quote"><div><br></div><div><br>Dear sajjad<br><br>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.<br></div><div>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.<br><br></div><div>I appreciate any comment on this from DFT experts.<br><br><br></div><div>Sincerely<br></div><div>Bhamu<br></div><div><br> </div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex"><div dir="ltr"><span class=""><div></div><div>I have computed PF for bulk Na and its value is <font color="#ff0000"><b>5.943 eV</b></font> with k-mesh <font color="#ff0000"><b>18*18*18</b></font>.</div><div><br></div></span><span class=""><div>Then I constructed a supercell 1*1*6 </div></span></div></blockquote><div><br></div><div><span style="color:rgb(0,0,255)">...>>>>>>> use 18*18*3 k points for 1*1*6 supercell. <br><br></span></div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex"><span class=""><div dir="ltr"><div>and run the calculation with different k-meshes and obtained PF values. The details are </div><div><br></div><div><b>K-mesh PF (x/z components in eV)</b></div><div><b><br></b></div><div><div><b>24*24*24 5.7097 / 5.8192</b></div><div><b><br></b></div><div><b>36*36*24 5.7614 / 5.8098 <br></b></div><div><b><br></b></div><div><b>50*50*10 5.9358 / 5.6280 <br></b></div><div><b><br></b></div><div><b>50*50*30 5.9365 / 5.8079</b><br></div><div> </div><div>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 <b><font color="#ff0000">PF = 5.943 eV</font></b> for the supercell and then, definitely, need more test calculation for right k-mesh selection?</div><span><font color="#888888"><div><br></div></font></span></div><span><font color="#888888">-- <br><div><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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<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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