Error when adding symmetry to a set of atoms in the ASU

[Leopoldo Suescun]

Hi,

I have a monoclinic C2/c structure that is also reported in I2/a (both unique axis b).

The C2/c is in cell choice 1 while I2/a is in cell choice 3.

I want to compare both to make sure they are the same. So I took the I2/a structure, removed symmetry keeping all atoms in the cell, transformed the unit cell (and atomic coordinates) using the Transformation Matrix in VESTA using the proper origin translation.

I end up with a P1 model with all atoms in the unit cell that looks identical that the C2/c model.

In the P1 model I have 4 or 8 copies of each atom from the C2/c model because a couple of atoms sit at 4a and 4e sites while others sit at general positions.

I located the same exact positions reported in the C2/c model in the P1 model atom list and deleted all that are not the "original" ones. Then I added symmetry to the P1 model in order to reproduce the C2/c structure, in order to make sure my transformation is correct. However, the resulting structure got atoms at impossible sites, e.g. one equivalent atom to 0,0,0 position shows at 0,1/2,0 which is not  in the 4a orbit.

Is there a bug in VESTA and I am getting the wrong result? Or am I doing something wrong, which I could not realize what since I would have done exactly what I explained by hand and had the right result.

I could provide the data, but the structures were taken from ICSD and they both correspond to Li2CuPO4 compound.

Thanks for any help anyone could provide.

Leo

[Maykel Manawan]

Dear Leo,

I'm not so sure until I try, but Vesta works perfectly with TiNb2O7 that have monoclinic C2/m that has various settings.

Please attach your CIF file.

Best Wishes

Maykel

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