ABINIT Discussion Forums

Hi all,

I am working with a cell that can either be expressed as primitive, monoclinic Pm or non-primitive (2 formula units), orthorhmobic Amm2. I want to use the larger, orthorhombic cell for a certain calculation, specifically because it has orthogonal lattice vectors.

To allow Abinit to complete the run, I need to put chkprim 0. The Bravais lattice is still identified as orthorhombic, but not the point group or space group. I would like to confirm that my cell is indeed Amm2 in the calculation, and also use that as a constraint during the relaxation. I tried matching the number of symmetry elements through counting the symrel matrices, but this isn't giving me the results I expected.

Is there a way to know this from the output files?

Cheers,
J

Dear Jerkov,
You need to analyze the relaxed cell with a program that will tell you the exact crystal space group in the case of supercell calculation. Abipy or qAgate are directly interfaced with Abinit and can do the job through the spglib python library. You can also use the FINDSYM software from ISTROPY (https://stokes.byu.edu/iso/findsym.php). I would say that if you did not make a mistake in the initial Abinit input position and cell parameter then chkprim keeps the right symmetries.
All the best,
Eric

Hi Eric,

Thanks for the suggestions. I confirmed the cell was Amm2 with a separate software, and I also made sense of the symrel printed by Abinit. As I said earlier, I only expected to see 4 matrices, not 8 as I do in the log file. However, each one is a duplicate, so there are only 4 different matrices, which I guess are printing twice because the multiplicity of the cell is 2. And as I just checked, there are only these 4 different matrices in the out file.
The symrel are the 4 elements of the Amm2 I expect to see, so we're good!

Cheers,
J

OK, great!
The symrel are indeed duplicated with a translation vector that you can see in the output file through tnons.
Best,
Eric