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
On 27 Feb 2024, at 11:36, Giovanni Cantele <[email protected]> wrote: Let us suppose that we have a fcc crystal, with one atom per cell, at (0,0,0), for the sake of simplicity. 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. Now, let us move from fcc to sc unit cell. Each of the 8 atoms at the corners is shared by 8 cubic cells, and thus we should consider only one of these atoms. 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 6 faces, 3 out of these 6 atoms must be considered. As a result, the sc unit cell will contain 4 atoms and a volume 4 times larger, a^3 as you would expect. 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, that should be explicitly considered in sc, now become equivalent (that is, connected by a lattice vector) to other atoms in fcc. 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) 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. Giovanni -- Giovanni Cantele, PhD CNR-SPIN c/o Dipartimento di Fisica Universita' di Napoli "Federico II" Complesso Universitario M. S. Angelo - Ed. 6 Via Cintia, I-80126, Napoli, Italy e-mail: [email protected]<mailto:[email protected]> Phone: +39 081 676910 Skype contact: giocan74 ResearcherID: http://www.researcherid.com/rid/A-1951-2009 Web page: https://sites.google.com/view/giovanni-cantele/home Il giorno mar 27 feb 2024 alle ore 11:14 Ms. Chandrika K. via users <[email protected]<mailto:[email protected]>> ha scritto: Need help in understanding 1. I am currently working on Co3O4 structure,from literature it is very evident that it belongs to space group Fd3m(cubic fcc). 2. 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. 3. As it is simple cubic ibrav =1,when i change ibrav =2(cubic fcc) i am getting warning message "WARNING: Atom 381 and atom 444 are very close !!! Atom 444 deleted !!!" ATOMIC_POSITIONS (angstrom) I would like to know how to change the structure from simple cubic to fcc cubic chandrika yadav k _______________________________________________ The Quantum ESPRESSO community stands by the Ukrainian people and expresses its concerns about the devastating effects that the Russian military offensive has on their country and on the free and peaceful scientific, cultural, and economic cooperation amongst peoples _______________________________________________ Quantum ESPRESSO is supported by MaX (www.max-centre.eu<http://www.max-centre.eu/>) users mailing list [email protected]<mailto:[email protected]> https://lists.quantum-espresso.org/mailman/listinfo/users _______________________________________________ The Quantum ESPRESSO community stands by the Ukrainian people and expresses its concerns about the devastating effects that the Russian military offensive has on their country and on the free and peaceful scientific, cultural, and economic cooperation amongst peoples _______________________________________________ Quantum ESPRESSO is supported by MaX (www.max-centre.eu) users mailing list [email protected] https://lists.quantum-espresso.org/mailman/listinfo/users — Stefano Baroni - Trieste — http://stefano.baroni.me
_______________________________________________ The Quantum ESPRESSO community stands by the Ukrainian people and expresses its concerns about the devastating effects that the Russian military offensive has on their country and on the free and peaceful scientific, cultural, and economic cooperation amongst peoples _______________________________________________ Quantum ESPRESSO is supported by MaX (www.max-centre.eu) users mailing list [email protected] https://lists.quantum-espresso.org/mailman/listinfo/users
