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[Masayoshi Mikami <mmikami@yk.rim.or.jp>]

Hello, 

The input for your crystal structure may have problems. 
Please take a look the table:
 http://www.cryst.ehu.es/cgi-bin/cryst/programs/nph-wp-list?gnum=194
At least, the multiplicity of the site (0, 0, 0) is two,
so the keywords "natom 3" "typat 1 2 2" seems strange ...

(The above table is obtained from the Bilbao Crystallographic Server:
   http://www.cryst.ehu.es/
 Kindly try "WYCKPOS -- Wyckoff Positions of Space Groups" 
 This site is cited in ~ABINIT/Infos/Miscellaneous/Crystals )

I do not know MgZn2 ... So that I consulted with "EMS on line".
  http://cimesg1.epfl.ch/CIOLS/crystal1.pl
(This site will be mentioned in the above file.)
"MgZn2 - Komura & Tokunaga 1980" can be found in the right list.
The crystal view of the MgZn2 can be confirmed on the WEB page...
(Hereafter... could you please check your input file ? 
 "abinis help" file and "input variables" file may also help you ...
 e.g. natrd ...)

Hope this helps,
Masayoshi



From: c.gross@physik.uni-frankfurt.de
Subject: [abinit-forum] Definition of hexagonal cell / MgZn2
Date: Tue, 22 Jul 2003 14:54:15 +0200
Message-ID: <sympa.1058877662.10212.14@abinit.org>

> Hello everybody,
> 
> this is (probably) a newbie question...
> 
> I am trying to define the unit cell of MgZn2 (primitive hexagonal) by the 
> following lines in my input file:
> 
> ------------
> 
> #Definition of the unit cell
> acell 5.223 5.223 8.5666 angstrom
> angdeg 90 90 120     # hexagonal cell
> spgroup 194          # space group no 194, P63/mmc
> 
> #Definition of the atom types
> ntypat 2             # Two types of atoms (Mg, Zn)
> znucl 12 30          # The keyword "znucl" refers...
>                          
> #Definition of the atoms
> natom 3              # There are three atoms
> typat 1 2 2          # First atom: type 1, second: type 2, third: type 2
> xred                 # This keyword indicate that the location of the atoms
>                      # will follow, one triplet of number for each atom
> 1/3 2/3 0.06286      # Triplet giving the REDUCED coordinate of atom 1 (Mg).
> 0.83048 0.66096 1/4  # Triplet giving the REDUCED coordinate of atom 2 
> (Zn2).
> 0 0 0                # Triplet giving the REDUCED coordinate of atom 3 
> (Zn1). 
> 
> (...)
> ------------
> 
> But, ABINIT sends lots of warnings of the following type to the log file 
> (and finally stops):
> 
> ------------
> 
>  symatm : WARNING -
>   Trouble finding symmetrically equivalent atoms
>   Applying inv of symm number  2 to atom number   1  of typat  1
>   gives tratom=  6.6667E-01  3.3333E-01 -4.3714E-01.
>   This is further away from every atom in crystal than the allowed 
> tolerance.
>   The inverse symmetry matrix is  0 -1  0
>                                   1  1  0
>                                   0  0  1
>   and the nonsymmorphic transl. tnons =    0.0000000    0.0000000    
> 0.5000000
>   The nearest coordinate differs by  3.333E-01 -3.333E-01  5.000E-01
>   for indsym(nearest atom)=    1
> 
>   This indicates that when symatm attempts to find atoms symmetrically
>   related to a given atom, the nearest candidate is further away than some
>   tolerance.  Should check atomic coordinates and symmetry group input data.
> 
> ------------
> 
> Is this a problem with my input file ? Am I using the SPGROUP command 
> correctly, or am I supposed to provide the positions of all atoms in the 
> unit cell, not just the asymmetric unit ?
> 
> I would be thankful for a hint,
> Christoph
>