[ase-users] Space group #68 and Sr3Ru2O7

[Jens Jørgen Mortensen]

tir, 20 09 2011 kl. 17:55 +0200, skrev "José C. Conesa":
> Hi,
> You might have two problems:
> 1-The "standard" way of specifying space group 68 is as Ccca which has 
> the centering lattice point in the ab plane; Bbcb is an alternative 
> description which has the axes taken in different order so that the 
> centering point is in plane ac. In order to get the Ccca description you 
> have to reorder axes so that e.g. the O3 atom has coordinates (0.09710  
> 0.5293 -0.0293). Maybe if you use this description you can obtain the 
> good structure.
> 2-I think that these cooordinates correspond to using setting 2. 
> Settings 1 and 2 differ in where the coordinate origin is taken.

Thanks a lot!  This now works:

from ase.lattice.spacegroup import crystal
a = 5.5006
c = 20.725
x = crystal('RuSr2O3',
            [(0.40298, 0.25, 0.25),
             (0.0, 0.25, 0.25),
             (0.18631, 0.25, 0.25),
             (0.5, 0.25, 0.25),
             (0.30448, 0.25, 0.25),
             (0.09710, 0.5293, -0.0293)],
            spacegroup=68,
            setting=2,
            cellpar=[c, a, a, 90, 90, 90])

Amazing!  What's the best thing for me to read if I want to understand
this stuff better?

> By the way, you may like to see a newer determination in the following 
> paper:
> Kiyanagi, R.; Tsuda, K.; Aso, N.; Kimura, H.; Noda, Y.; Yoshida, Y.; 
> Ikeda, S.I.; Uwatoko, Y.
> Journal of the Physical Society of Japan (2004) 73, 639-642

Thanks for this link also.

Jens Jørgen

> Here the two short axes are not equal. On the other hand, atom O4 is not 
> used, and atom O3 has full occupation.
> Good luck
> 
> El 20/09/2011 14:28, Jens Jørgen Mortensen escribió:
> > Can anyone here help me build the Sr3Ru2O7 structure described here:
> >
> > http://www.sciencedirect.com/science/article/pii/S0022459600987966
> >
> > Table 2 says something like this:
> >
> > Atom  x       y      z       fraction
> > Ru    1/4     1/4    0.40298 1
> > Sr1   1/4     1/4    0       1
> > Sr2   1/4     1/4    0.18631 1
> > O1    1/4     1/4    1/2     1
> > O2    1/4     1/4    0.30448 1
> > O3    0.5293 -0.0293 0.09710 0.959
> > O4    0.4707  0.0293 0.09710 0.041
> >
> > a=5.5006 Å, b=5.5006 Å, c=20.725 Å
> > Space group: Bbcb (#68)
> >
> > I tried:
> >
> > from ase.lattice.spacegroup import crystal
> > a = 5.5006
> > c = 20.725
> > x = crystal('RuSr2O3',
> >              [(0.0, 0.0, 0.40298),
> >               (0.25, 0.25, 0.0),
> >               (0.25, 0.25, 0.18631),
> >               (0.25, 0.25, 0.5),
> >               (0.25, 0.25, 0.30448),
> >               #(0.5293, -0.0293, 0.09710),
> >               (0.4707, 0.0293, 0.09710)],
> >              spacegroup=68,
> >              #setting=1,
> >              cellpar=[a, a, c, 90, 90, 90])
> > x.edit()
> >
> > But I must admit, I have no idea what I am doing.  I get this warning:
> >
> > /home/jensj/ase/ase/lattice/spacegroup/spacegroup.py:375: UserWarning:
> > scaled_positions 1 and 3 are equivalent
> >    'are equivalent'%(kinds[ind], kind))
> >
> > and the structure I get has too many atoms.  Any idea what I am doing
> > wrong?
> >
> > Jens Jørgen
> >
> >
> >
> >
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