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Atom position (coordinates) from symmetry

  1. Sep 11, 2010 #1
    Hi guys,
    I need to write down the positions of all the atom in LaFeAsO unit cell:

    nature07045-f1.2.jpg
    Figure caption: "The quaternary equiatomic ZrCuSiAs-type structure is very simple, with only eight atoms in the tetragonal cell. The dashed lines represent a unit cell."

    I also have these informations about ZrCuSiAs

    Atom Posit x y z

    Zr 2c 1/4 1/4 0.2246
    Cu 2b 1/4 3/4 1/2
    Si 2a 1/4 3/4 0
    As 2c 1/4 1/4 0.6793


    Space group: P4/nmm.

    So...starting from the figure above is easy to get the coordinates of Fe and O atoms but what about Sm and As?
    And what's the relationship between the image and the positions reported above (and note that the pictures reported in the article about ZrCuSiAs and the above one from nature are different! http://img541.imageshack.us/img541/3563/zrcusias.jpg" [Broken])

    And last but not least...is there a tool to automate this process? Writing down all x,y,z is really boring!:)

    Thanks
    Pietro
     
    Last edited by a moderator: May 4, 2017
  2. jcsd
  3. Sep 13, 2010 #2
    Ok, the two upper green balls are in the left and right faces, then b=0 and b=1. Both are at half face, a=1/2. And height c is 1/2 plus "x" were x you should find aplying trigonometrics. Maybe d Fe-As = SQROOT(2)*x
    The lower green balls are almost the same a=1 a=0, b=1/2 c=(1/2)-x

    And for the blue ones the same.
     
  4. Sep 20, 2010 #3
    Hi,
    Have a look at this site
    http://cst-www.nrl.navy.mil/lattice/struk/FeS2.html [Broken]

    There are are some coordinates for writing x,y, and z values.
    e.g., few are: cartesian, internal coordinates, and z-matrics.

    May for visualization you can use MOLDEN or Avogadro (both are free)
     
    Last edited by a moderator: May 4, 2017
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