[Wien] Vacancy problem with Wien2k

[Jorissen Kevin]

I'm not sure about this part of symmetry, but often (eg in nn), wien will generate internally more positions by repeating the unit cell.  This is useful (in the initialization) to determine the surroundings and local symmetry of your atoms.  It does not mean that these extra atoms will actually be considered in the scf calculation (except through periodic boundary conditions, of course).
If you want to know the total number of atoms in your unit cell, check case.outputsgroup.  Somewhere in the beginning of this file, the total number of atoms is mentioned.  If that says 88, you're alright.
 
Kevin.
 
 

	-----Oorspronkelijk bericht----- 
	Van: Daniel Kmiec [mailto:kmiec at ap.univie.ac.at] 
	Verzonden: ma 3/1/2004 10:35 
	Aan: wien at zeus.theochem.tuwien.ac.at 
	CC: 
	Onderwerp: [Wien] Vacancy problem with Wien2k
	
	

	Dear Wien2k users,
	
	I am quit new user of Wien2k, I tried to find answer for my question
	in usersguide an mailing list but without luck.
	Since some time I'm trying to calcute a surface system with a vacancy.
	
	(for good display please use fixed font width)
	This shows, how one layer looks like?
	It is bcc 110 surface
	O - vacancy
	* - atom
	
	top view of the surface
	
	O ----------- * ----------- * ----------- O
	|             |             |             |
	|      *      |      *      |      *      |
	|             |             |             |
	* ----------- * ----------- * ----------- *
	|             |             |             |
	|      *      |      *      |      *      |
	|             |             |             |
	* ----------- * ----------- * ----------- *
	|             |             |             |
	|      *      |      *      |      *      |
	|             |             |             |
	O ----------- * ----------- * ----------- O
	
	I have 5 such layers defined
	
	vacum
	surface   .................
	substrate -----------------
	substrate -----------------
	substrate -----------------
	surface   .................
	vacum
	
	The vacancy is only on surface, the substrate contains all atoms.
	
	Now comes my question, when I'm not wrong in this case I should have 18
	atoms per layer(or 17 + vacancy on the surface). This gives the total
	number of atoms 88 + 2 vacancies. The symetry group I have in this case
	is Pmmm and I have 23 inequivalent atoms.
	Maybe this is a silly question but in "case.outputs" file I found line
	which says that the number of atom is 352 (also 4 times bigger).
	
	After the list of all 88 atoms with positions comes section:
	
	DETERMINATION OF POINTGROUP FOR ALL POSITIONS
	and there i see lines like this
	...
	Fe        :  16 Atoms, Index  337 to  352
	number of atoms: 352
	...
	
	I would like to know what is Wien2k doing here? It tries to generate all
	possible positions of atoms, and then reduce the total number to only
	inequivalent ones ? I hope it is calculating _only_ the cell with 88 atoms.
	
	Best regards
	Daniel Kmiec
	
	--
	____________________________________________________
	Daniel Kmiec
	Institut für Materialphysik
	Strudlhofgasse 4              Tel : +43 1 4277 51310
	1090 Wien, Austria            Fax : +43 1 4277 9513
	
	
	
	
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