Dear QE, I'm wondering what ibrav means in pw.x. My confusion is that if you can specify atomic positions freely, isn't the structure of the solid already implied by the positions? So why do we need the extra variable of ibrav. Or does ibrav carries more meaning than just the initial lattice structure of the solid?
Another related question: When I ran vc-relax, I specified ibrav = 2 (fcc) and the atomic positions as follows: ATOMIC_POSITIONS {alat} Al 0.0 0.5 0.5 Al 0.5 0.0 0.0 Al 0.25 0.25 0.25 Al 0.0 0.5 0.0 Ti 0.75 0.75 0.75 Ti 0.5 0.0 0.5 Cr 0.0 0.0 0.0 Cr 0.75 0.75 0.25 Fe 0.5 0.5 0.0 Fe 0.75 0.25 0.25 Co 0.0 0.0 0.5 Co 0.25 0.75 0.25 Co 0.75 0.25 0.75 Ni 0.25 0.75 0.75 Ni 0.25 0.25 0.75 Ni 0.5 0.5 0.5 QE erred and complained that atom #1 and atom #6 overlap, which they apparently don't from the first sight. When I set ibrav = 1 (sc) and kept the same atomic positions, the complaint disappeared. So does anyone know why did the error occur? I appreciate your replies with all my gratitude. Yantao "ignorant student" Wu -------------- next part -------------- An HTML attachment was scrubbed... URL: http://pwscf.org/pipermail/pw_forum/attachments/20130528/6bed12f5/attachment.html