AFM calculations

Dear Abinit Community,

Currenlty I am working in a system with Fe atoms using antiferromagnetism, the so called “single-layer antiferromagnetic (afmI) face centered tetragonal (fct) state”. The results of the lattice parameters and elastic constants agree well with literature. Details of the calculation can be found on the attached log file (AFM_Fe.log)

Now I am trying to check the influence of a substitutional Cr atom in such system, so one Fe atom is replaced by Cr. Unfortunately, abinit gives the following error when the simulation is run (see also attached log file, AFM_Fe_Cr.log):

chkinp: Checking input parameters for consistency, jdtset=   1.
When nsppol==1 and nspden==2, at least one of the symmetry operations
must be anti-ferromagnetic (symafm=-1), in order to deduce the spin-down density
from the spin-up density.

--- !ERROR
src_file: m_chkinp.F90
src_line: 2939
mpi_rank: 0
message: |
    However, it is observed that none of the symmetry operations is anti-ferromagnetic.
    Action: Check the atomic positions, the input variables spinat, symrel, tnons, symafm.
            In case your system is not antiferromagnetic (it might be ferrimagnetic ...),
            you must use nsppol=2 with nspden=2 (the latter being the default when nsppol=2).

The initial spins are kept the same as for the case of pure Fe, so I do not really understand why the anti-ferromagnetic symmetry is broken.

Any comments/suggestions are much appreciated.

AFM_Fe_Cr.log (47.4 KB)
AFM_Fe.log (3.4 MB)

Hi Sebastian,

your spin texture is AFM, but the atoms are not the same species (Cr is not Fe) so they are not symmetric. They probably don’t even have the same moments, so your net M is not 0

E.g. you probably only have 1 Cr atom, which is either up or down, and can not be in an AFM state (for which you need net 0 magnetization and all up and down atoms to correspond through some spatial symmetry). Just put nspden 2 nsppol 2 so it is free to break the exact AFM condition.