[Pw_forum] query

[Giovanni Cantele]

> On 25 May 2017, at 12:08, aprateek at iisermohali.ac.in wrote:
> 
> 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. ?
> 
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Maybe in the last for positions you meant 0.5, not 5.0. By the way, there is no algorithm, but simply at each ibrav
corresponds a lattice. For example ibrav=1 corresponds to a simple cubic lattice. The list of ibrav <-> lattice
correspondences can be found here:
http://www.quantum-espresso.org/wp-content/uploads/Doc/INPUT_PW.html#idm140629872541472 <http://www.quantum-espresso.org/wp-content/uploads/Doc/INPUT_PW.html#idm140629872541472>

It is true that the lattice sites of a face centered lattice can be described, besides using the obvious face centred lattice,
with a simple cubic lattice with four atoms in the unit cell.

I suggest you to read the relevant documentation/tutorials that are available.

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: giovanni.cantele at spin.cnr.it
Phone: +39 081 676910
Skype contact: giocan74

ResearcherID: http://www.researcherid.com/rid/A-1951-2009
Web page: http://people.fisica.unina.it/~cantele

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