On Thu, Dec 17, 2009 at 11:04 AM, Lorenzo Paulatto <paulatto at sissa.it> wrote: > Replying to message "[Pw_forum] Fwd: different symmetry when using > equivalent representation" from Jess Kondor (17/12/09): >> ?I have some trouble in understanding why equivalent (if I am not >> wrong) representation of the crystal structure leads to different >> symmetry (as shown in the output from pw.x). All input/output >> files are attached. > > Dear Jess, > the code threshold for checking the symmetry is too strict for the number > of significant digits you have specified for the basis vectors (I see you > have copied them from the output of test1.inp, but apparently it is not > enough). > > You recover all 6 symmetry operations if you specify the cell parameters > with more digits, e.g. > ? ?0.502718227240668 ?-0.290244503823931 ? 0.814268083618657 > ? ?0.000000000000000 ? 0.580489007647862 ? 0.814268083618657 > ? -0.502718227240668 ?-0.290244503823931 ? 0.814268083618657 > > best regards > > -- > Lorenzo Paulatto > SISSA ?& ?DEMOCRITOS (Trieste) > phone: +39 040 3787 511 > skype: paulatz > www: ? http://people.sissa.it/~paulatto/ > > ? ? *** save italian brains *** > ?http://saveitalianbrains.wordpress.com/ > _______________________________________________ > Pw_forum mailing list > Pw_forum at pwscf.org > http://www.democritos.it/mailman/listinfo/pw_forum >
Dear Lorenzo, Thanks a lot for the solution. How many digits do I need? I agree, that output basis vectors are printed with 6 significant digits and this is not enough. However, if I change 'scf' to 'vc-relax', the code prints CELL_PARAMETERS with much more digits (9), and this is still not enough to find all 6 symmetries. 0.502718227 -0.290244504 0.814268084 0.000000000 0.580489008 0.814268084 -0.502718227 -0.290244504 0.814268084 Probably, it is better to change a source code to print more digits in order to allow simple cut/and/paste from output/to input without using extra tools? Thanks a lot! -- ===================================== Jess Kondor NSTI =====================================
