On Wed, Dec 11, 2013 at 7:47 PM, Reza Behjatmanesh-Ardakani <reza_b_m_a at yahoo.com> wrote: > Suppose, we have a simple fcc unit cell. Do we need to introduce one > particle position (original particle) or 14 particles (8 on corners and 6 on > the faces). I think only originals needed. Other particles can be produced > by symmetry operators.
nope. a fcc lattice has only one atom. that is in the *primitive* cell (which is what QE uses). what you describe is the conventional cell, which would be a simple cubic lattice but that would not have 14 atoms but 4 atoms (1 in the corner and 3 in the faces, because the corners are shared by 8 cells and the faces by 2). i suggest you re-read the chapters covering these topics in your favorite book on crystallography to work this out. axel. > > With the Best Regards > > > Reza Behjatmanesh-Ardakani > Associate Professor of Physical Chemistry > Address: > Department of Chemistry, > School of Science, > Payame Noor University (PNU), > Ardakan, > Yazd, > Iran. > E-mails: > 1- reza_b_m_a at yahoo.com (preferred), > 2- behjatmanesh at pnu.ac.ir, > 3- reza.b.m.a at gmail.com. > > > On Wednesday, December 11, 2013 7:19 PM, Paolo Giannozzi > <paolo.giannozzi at uniud.it> wrote: > On Wed, 2013-12-11 at 07:12 -0800, Reza Behjatmanesh-Ardakani wrote: > >> 1- For preparing the input file, if you introduce a symmetry in your >> input's structure, only original particles >> should be defined in the input file. Is it right? > > no: you need to supply all atoms in a unit cell. > > > P. > > -- > Paolo Giannozzi, Dept. Chemistry&Physics&Environment, > Univ. Udine, via delle Scienze 208, 33100 Udine, Italy > Phone +39-0432-558216, fax +39-0432-558222 > > > > > > _______________________________________________ > Pw_forum mailing list > Pw_forum at pwscf.org > http://pwscf.org/mailman/listinfo/pw_forum -- Dr. Axel Kohlmeyer akohlmey at gmail.com http://goo.gl/1wk0 International Centre for Theoretical Physics, Trieste. Italy.
