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Thank you Giovanni. May I suggest that in this and other similar cases help from the Quantum ESPRESSO Community is properly acknowledged in any work (thesis, paper, report) that has benefited from it? Thanks — Stefano
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<div>On 27 Feb 2024, at 11:36, Giovanni Cantele <giovanni.cantele@spin.cnr.it> wrote:</div>
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<div dir="ltr">Let us suppose that we have a fcc crystal, with one atom per cell, at (0,0,0), for the sake of simplicity.
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<div>The unit cell sides are in the form (a/2,a/2,0) (a=side of the cubic cell), with unit cell volume a^3 / 4.</div>
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<div>Now, let us move from fcc to sc unit cell. </div>
<div>Each of the 8 atoms at the corners is shared by 8 cubic cells, and thus we should consider only one of these atoms.</div>
<div>On the other hand, atoms at the center of the cube faces are shared by two unit cells, and count as 1/2. Since we have</div>
<div>6 faces, 3 out of these 6 atoms must be considered.</div>
<div>As a result, the sc unit cell will contain 4 atoms and a volume 4 times larger, a^3 as you would expect.</div>
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<div>To go back from sc to fcc you should therefore keep 1/4 of your atoms, because those that are associated to the centers of three faces,</div>
<div>that should be explicitly considered in sc, now become equivalent (that is, connected by a lattice vector) to other atoms in fcc.</div>
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<div>The code correctly finds overlapped atoms, e.g. in the example of one atom per unit cell, in sc you would have (0,0,0), (a/2,a/2,0), (a/2,0,a/2), (0,a/2,a/2)</div>
<div>and the last three in fcc are obtained from (0,0,0) after a lattice translation by (a/2,a/2,0), (a/2,0,a/2), (0,a/2,a/2), respectively.</div>
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<div>Giovanni</div>
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<div dir="ltr"><span style="">-- <br>
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Giovanni Cantele, PhD<br>
CNR-SPIN<br>
c/o Dipartimento di Fisica<br>
Universita' di Napoli "Federico II"<br>
Complesso Universitario M. S. Angelo - Ed. 6<br>
Via Cintia, I-80126, Napoli, Italy<br>
<a href="mailto:giovanni.cantele@spin.cnr.it" style="color:rgb(17,85,204)" target="_blank">e-mail: giovanni.cantele@spin.cnr.it</a><br>
Phone: +39 081 676910<br>
Skype contact: giocan74<br>
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ResearcherID: <a href="http://www.researcherid.com/rid/A-1951-2009" style="color:rgb(17,85,204)" target="_blank">http://www.researcherid.com/rid/A-1951-2009</a><br>
Web page: </span><a href="https://sites.google.com/view/giovanni-cantele/home" style="color:rgb(17,85,204)" target="_blank">https://sites.google.com/view/giovanni-cantele/home</a><br>
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<div dir="ltr" class="gmail_attr">Il giorno mar 27 feb 2024 alle ore 11:14 Ms. Chandrika K. via users <<a href="mailto:users@lists.quantum-espresso.org">users@lists.quantum-espresso.org</a>> ha scritto:<br>
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<div><span style="font-family: Aptos, Aptos_EmbeddedFont, Aptos_MSFontService, Calibri, Helvetica, sans-serif; font-size: 12pt;">Need help in understanding </span></div>
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<span style="font-family: Aptos, Aptos_EmbeddedFont, Aptos_MSFontService, Calibri, Helvetica, sans-serif; font-size: 12pt;">I am currently working on Co3O4 structure,from literature it is very evident that it belongs to space group Fd3m(cubic fcc).</span></li><li style="font-family: Aptos, Aptos_EmbeddedFont, Aptos_MSFontService, Calibri, Helvetica, sans-serif; font-size: 12pt;">
<div style="margin:0px"><span style="font-family: Aptos, Aptos_EmbeddedFont, Aptos_MSFontService, Calibri, Helvetica, sans-serif; font-size: 12pt;">I have referred to Co3O4 Fd3m cubic structure from materials project it is represented as simple cubic structure
but Fd3m space group refers to cubic fcc.</span></div>
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<div style="margin:0px"><span style="font-family: Aptos, Aptos_EmbeddedFont, Aptos_MSFontService, Calibri, Helvetica, sans-serif; font-size: 12pt;">As it is simple cubic ibrav =1,when i change ibrav =2(cubic fcc) i am getting warning message </span></div>
<div style="margin:0px"><span style="font-family: Aptos, Aptos_EmbeddedFont, Aptos_MSFontService, Calibri, Helvetica, sans-serif; font-size: 12pt;">"WARNING: Atom 381 and atom 444 are very close !!! Atom 444 deleted !!!"</span></div>
<div style="margin:0px"><span style="font-family: Aptos, Aptos_EmbeddedFont, Aptos_MSFontService, Calibri, Helvetica, sans-serif; font-size: 12pt;">ATOMIC_POSITIONS (angstrom)</span></div>
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I would like to know how to change the structure from simple cubic to fcc cubic</div>
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chandrika yadav k </div>
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_______________________________________________<br>
The Quantum ESPRESSO community stands by the Ukrainian<br>
people and expresses its concerns about the devastating<br>
effects that the Russian military offensive has on their<br>
country and on the free and peaceful scientific, cultural,<br>
and economic cooperation amongst peoples<br>
_______________________________________________<br>
Quantum ESPRESSO is supported by MaX (<a href="http://www.max-centre.eu/" rel="noreferrer" target="_blank">www.max-centre.eu</a>)<br>
users mailing list <a href="mailto:users@lists.quantum-espresso.org" target="_blank">
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_______________________________________________<br>
The Quantum ESPRESSO community stands by the Ukrainian<br>
people and expresses its concerns about the devastating<br>
effects that the Russian military offensive has on their<br>
country and on the free and peaceful scientific, cultural,<br>
and economic cooperation amongst peoples<br>
_______________________________________________<br>
Quantum ESPRESSO is supported by MaX (www.max-centre.eu)<br>
users mailing list users@lists.quantum-espresso.org<br>
https://lists.quantum-espresso.org/mailman/listinfo/users</div>
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<div><span style="font-size: 12px;">— </span></div>
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<div style="margin: 0px;"><font class="Apple-style-span"><span style="font-size: 12px;">Stefano Baroni - Trieste — </span><a href="http://stefano.baroni.me" style="color: rgb(0, 0, 0); font-family: Helvetica; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; text-transform: none; white-space: normal; word-spacing: 0px; -webkit-text-decorations-in-effect: none; -webkit-text-stroke-width: 0px;">http://stefano.baroni.me</a><span style="font-size: 12px;"> </span></font></div>
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