<div dir="ltr"><div>Hi,</div><div> Always compare the energy per formula unit, if you do that in your case there is a small different in energy which may be due to different k-grid and energy cutoff. <br></div><div> I think it is better to optimize the kpoints and energy cutoff for particular unit cell or supercell.<br></div></div><br><div class="gmail_quote"><div dir="ltr" class="gmail_attr">On Sun, Jan 19, 2020 at 2:55 AM Manu Hegde <<a href="mailto:mhegde@sfu.ca">mhegde@sfu.ca</a>> wrote:<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"><div class="gmail_default" style="font-family:arial,helvetica,sans-serif">Hi Pooja,</div><div class="gmail_default" style="font-family:arial,helvetica,sans-serif">I think CaO is a cubic crystal. You can use VESTA to generate a supercell. It can take .cif file. Play with it. I believe extending lattice parameter 2X2X2 generate a 36 atom supercell. </div><div class="gmail_default" style="font-family:arial,helvetica,sans-serif">HTH</div><div class="gmail_default" style="font-family:arial,helvetica,sans-serif">Manu</div><div class="gmail_default" style="font-family:arial,helvetica,sans-serif">(McMaster University)</div></div><br><div class="gmail_quote"><div dir="ltr" class="gmail_attr">On Sat, Jan 18, 2020 at 12:38 AM Pooja Vyas <<a href="mailto:poojavyas1251995@gmail.com" target="_blank">poojavyas1251995@gmail.com</a>> wrote:<br></div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex">
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<div dir="ltr">
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<div>Respected sir/madam,</div>
<div>Referring a paper on calculation of energy with vacancy in CaO, I want to re-calculate the energy with the same number of atoms used in the paper.<br>
</div>
<div>They have 36 atoms in their supercell, 3 x 3 x 2 monk horst pack grid. From this information, is it possible to know what could be the value of n, in n x n x n supercell and what could be the initial number of atomic positions defined?</div>
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<div dir="ltr" class="gmail_attr">On Thu, Jan 16, 2020 at 11:58 AM Laurent Pizzagalli <<a href="mailto:laurent.pizzagalli@univ-poitiers.fr" target="_blank">laurent.pizzagalli@univ-poitiers.fr</a>> wrote:<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>Well, maybe because in your first calculation you had two atoms, and 64 in the second one.....You should try to see if multiplying -107.10 by 64/2 improve the comparison....<br>
<br>
L. <br>
<br>
<div>On 16/01/2020 06:23, Pooja Vyas wrote:<br>
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<div>Initially I had run my input script with ecut=100Ry and k-points= 11 11 11 1 1 1. At that time my energy was -107.10Ry. During this run, I had specified only two atomic positions (Ca: 0 0 0, O: 0.5 0.5 0.5)<br>
</div>
<div>For the same system but with ecut=60Ry and k-points= 3 3 3 1 1 1 the calculated energy was -3427.40Ry. During this run, I had specified 64 atomic positions.</div>
<div>Why does total energy value vary so much?<br>
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