Valeria: your question is answered, e.g., at page 10 of the eighth edition of Kittel’s solid state textbook. I am afraid you’ll have to go through as many as 9 pages to arrive at the point, but they are full of figures. Hope this helps. SB
___ Stefano Baroni, Trieste -- http://stefano.baroni.me > On 31 Jan 2021, at 07:39, Husak Michal <[email protected]> wrote: > > Forget this method. > Get a CIF file for the structure you want to stady and > use the space group based crystal definition ... > ________________________________ > From: users <[email protected]> on behalf of valeria > arteaga muñiz <[email protected]> > Sent: Sunday, January 31, 2021 5:26:37 AM > To: [email protected] > Subject: [QE-users] crystal definition > > Hello everyone. > > I have been working for a couple of months with quantum espresso and still > there are some things that get me confused. I hope you can help me. > If we wanted to define a BCC crystal (lets say) we could make use of the > ibrav=3 parameter. With this, we would have a bcc structure with one atom per > cell (?). I don’t know how can that be possible if the bcc cell is supposed > to have two atoms per cell (1/8 contribution of 8 corner atoms + 1 > contribution of a middle atom). When I use xcrysden for visualization just > setting ibrav =3, I get the complete bcc structure. > > I also have tried to create my bcc crystal from scratch using ibrav=0 and > placing the atomic positions at the corner and other atom at 0.5 0.5 0.5 > (center), which leads to 2 atoms per unit cell. When I make scf calculations > for this case I get around twice the total energy I get in previous case > (using ibrav=3). I wonder what is the correct way to use this. > > > Thanks for your clarifications, > Valeria > > _______________________________________________ > Quantum ESPRESSO is supported by MaX (www.max-centre.eu) > users mailing list [email protected] > https://lists.quantum-espresso.org/mailman/listinfo/users _______________________________________________ Quantum ESPRESSO is supported by MaX (www.max-centre.eu) users mailing list [email protected] https://lists.quantum-espresso.org/mailman/listinfo/users
