[Pw_forum] query

[aprateek at iisermohali.ac.in]

Hi,
I am beginner in using Quantum Espresso. I am giving coordinates of one
atom (Si 0.0 0.0 0.0) in angstrom/crystal.
With ibrav=1 it forms Simple Cubic
With ibrav=2 it forms Face Centred Cubic
With ibrav=3 it forms Body Centred  Cubic
and with ibrav=1 and
Si 0.0 0.0 0.0
Si 5.0 5.0 0.0
Si 5.0 0.0 5.0
Si 0.0 5.0 5.0

it forms face centred lattice. I would like to know the algorithim which
Xcrysden follows during visualization?

what if I want to control the no of atoms 3 or 4 in a Unit cell. ?