The structure is still wrong. You should "see" it in xcrysden. The atoms must be at (0,0), (1/3,2/3) and (2/3,1/3) (A,B,C) and not at (1/3,1/3),...
You cannot simply change the angle gamma from 60 to 120 without changing also the positions. I think it is pretty simple: Create the structure with octave (same way as you did before). Run sgroup and accept the structure. It gives a nice hexagonal structure. Am 08.09.2010 14:26, schrieb Bartosz Slomski: > After executing x sgroup with my initial Pbslab_34_34.struct I get the > warning: !!! Bravais lattice has changed. > sgroup found: 12 (C 2/m) [unique axis c] cell choice 2. > > > When I accept the structure of x sgroup, then the resulting structure > (Pb495_after_symmetry.struct) looks completely different from the original > one (Pbslab_34_34.struct) > > But, when I take the Au example and go through the initialization then the > message out of sgroup is just. symmetry group found sgroup 164 (P -3m 1) > > So there must be something wrong in my initial structure that I dont > understand. > > When I create the slab with octave and load into structgen then StructGen > says about the lattice: nie_mam pojecia, which means, "dont know the > spacegroup", then I edit the > struct.file to lattice H and change gamma from 60? to 120?. > But then I get the error: incorrect space group symbol. > > Sorry for boreing you with all these questions and problems...perhabs > somebody can provide me the commands to produce a 111 surface? > > With best regards, > > Bartosz > > > > Peter Blaha wrote: >> The procedure is ok. But you should accept the changes of sgroup ! >> It will move the origin so that you have inversion symmetry. >> >> Am 08.09.2010 12:15, schrieb Bartosz Slomski: >>> Dear Mr Blaha, >>> >>> indeed my structure does not represent a surface along [111]. >>> I made a mistake using structgen/octave. Instead of using makeconventional >>> one should use "makeprimitive" >>> Afterwards one has to change in StructGen the gamma angle to 120? and >>> select lattice type H. >>> >>> The final structure (Pb_slab_34_34.struct) has the stacking of A-B-C but >>> still differs slightly from the Au example. >>> In the Au example there is vacuum between the 12th layer and the 13th >>> layer, or are the layers 13..24 just the repeated unit cell of layer 1..12? >>> >>> During initialization of the Pb_slab I get the warning: you must move the >>> origin. >>> >>> Perhabs the procedure to generate a surface along [111] is still wrong. >>> >>> Thanks and best regards. >>> >>> >>> Peter Blaha wrote: >>>> Have you looked how the generated structure looks like ? (xcrysden) >>>> >>>> It is not correct. >>>> >>>> I'm not the expert with structgen and thus cannot tell you, where the >>>> error is. >>>> >>>> In any case, an fcc-111 surface is very easy (although one cannot use >>>> directly the supercell program). >>>> >>>> Have a look into example_struct_files/Gold_23l.struct >>>> This is an fcc 111 structure. All you need to do is to adjust the >>>> lattice parameters and eventually delete some of the atoms (if you want >>>> just >>>> 6 layers instead of 23). >>>> >>>> Remember the stacking: A-B-C .... ! >>>> >>>> PS. In general it is NOT a good idea to neglect warnings/errors/suggestions >>>> from nn or sgroup, unless "you know why you are doing it". >>>> >>>> A 6-layer slab has inversion symmetry and only 6 atoms/cell ! >>>> It runs in a couple of minutes, not 19 h. >>>> >>>> >>> >>> >>> >>> _______________________________________________ >>> Wien mailing list >>> Wien at zeus.theochem.tuwien.ac.at >>> http://zeus.theochem.tuwien.ac.at/mailman/listinfo/wien >> > > > > > _______________________________________________ > Wien mailing list > Wien at zeus.theochem.tuwien.ac.at > http://zeus.theochem.tuwien.ac.at/mailman/listinfo/wien -- P.Blaha -------------------------------------------------------------------------- Peter BLAHA, Inst.f. Materials Chemistry, TU Vienna, A-1060 Vienna Phone: +43-1-58801-15671 FAX: +43-1-58801-15698 Email: blaha at theochem.tuwien.ac.at WWW: http://info.tuwien.ac.at/theochem/ --------------------------------------------------------------------------
