On Jan 19, 2008, at 19:13 , Hongbin Zhang wrote: > 1) if the symmetry will be kept, then how can I break the symmetry if > necessary?
try with a hammer :-) Seriously: move one or a few atoms away from their symmetric positions > 2) I think there is a Keyword "nosym" in the namelist "&SYSTEM", is it > somehow related to structure relaxation? what the "nosym" option (a very misleading name in my opinion) does is explained in detail and exactly in the INPUT_PW file. Do not use it unless you understand it. > 3) In "ATOMIC_POSITIONS" catalog, it's possible to set "if_pos" terms, > which will make forces along some directions to be zero. How should I > combine these options with "nosym" option? these two options do not interact at all > 1) optimization with mirror symmetry along z direction > > 2) optimization without mirror symmetry along z direction > > So if the original supercell have the z-mirror symmetry, how to > break it > if relaxation will keep all symmetry pwscf find (nicola)? move just one atom from (x,y,z) to (x,y,z+dz), with dz > 10^(-5) *lattice parameter Paolo --- Paolo Giannozzi, Dept of Physics, University of Udine via delle Scienze 208, 33100 Udine, Italy Phone +39-0432-558216, fax +39-0432-558222
