FYI, the subprogram that does that is spacegroup (refer to section "9.14 spacegroup" in the WIEN2k 14.2 usersguide on page 195 [ http://www.wien2k.at/reg_user/textbooks/usersguide.pdf ]).

For example, Ti has the nonequivalent position (0,0,0), and it should have a Ti equivalent position of (0.5,0.5,0.5), as taken from TiO2.struct [ https://github.com/hpcugent/easybuild-easyconfigs/blob/master/easybuild/easyconfigs/w/WIEN2k/TiO2.struct ]:

TiO2
P   LATTICE,NONEQUIV.ATOMS: 2136_P42/mnm
MODE OF CALC=RELA unit=bohr
   8.682000  8.682000  5.592000 90.000000 90.000000 90.000000
ATOM -1: X=0.00000000 Y=0.00000000 Z=0.00000000 <= Nonequivalent Ti position
           MULT= 2          ISPLIT= 8
       -1: X=0.50000000 Y=0.50000000 Z=0.50000000 <= Equivalent Ti position
Ti         NPT=  781  R0=0.00005000 RMT=    2.0000   Z: 22.0
...

Run the WIEN2k spacegroup program in a terminal:

username@computername:~/wiendata/TiO2$ spacegroup
Type in cell parameters : 8.682000 8.682000 5.592000 90.000000 90.000000 90.000000
 Type in space group symbol : P42/mnm
 Name of the 1st atom : Ti
 Coordinates of the 1st atom : 0.00000000 0.00000000 0.00000000
 Ti/1        0.00000000  0.00000000  0.00000000
Ti/2 0.50000000 0.50000000 0.50000000 <= Here, it found the equivalent Ti position to be (0.5,0.5,0.5) as expected (for the 2a site [ http://www.cryst.ehu.es/cgi-bin/cryst/programs//nph-wp-list?gnum=136&what=wpos ]).
 Name of the 2nd atom :
username@computername:~/wiendata/TiO2$

If you prefer a Windows graphic user interface, there is the EQUIV program [ http://www.ccp14.ac.uk/tutorial/lmgp/equiv.htm ]. I believe EQUIV might be based on the getspec code [ http://www.iucr.org/resources/other-directories/software/getspec ].

I'm not aware of any article describing the insides of the spacegroup program or how it was written. It is likely, though, that the "International Tables for Crystallography" [ http://dx.doi.org/10.1107/97809553602060000001 ] were used as a reference.

Try searching journals out there related to computational crystallography. For example, the Journal of Applied Crystallography might be a good one to search [ http://dx.doi.org/10.1107/S0021889875011004 , http://dx.doi.org/10.1107/S0021889804031528 ].

On 2/15/2016 7:28 AM, Tomas Kana wrote:

Dear Amir,

At first, you should specify the structure using the Space group number

(for example in w2web or makestruct_lapw). Then, you specify only

one position and the remaining positions (belonging to the space group)

are generated automatically.

Hope this helps

Tomas


    Dear WIEN2k users,
    Please let me know
    How can i generate equivalent positions for a atom or different
    atoms  for a compound with a specific symmetry?
    I would like to know background of it for writing a program.
    Sincerely,
    Amir

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