Spin with Abinit
An example of visualising antiferromagnetic spin in FeO with Abinit.
The input files used for abinit were:FeO.in
acell 16.372587151 8.18629357548 8.18629357548 rprim 0.00000000000 0.50000000000 0.50000000000 0.50000000000 0.00000000000 0.50000000000 0.50000000000 0.50000000000 0.00000000000 ntypat 2 znucl 8 26 natom 4 typat 1 1 2 2 xred 0.25 0.5 0.5 0.75 0.5 0.5 0 0 0 0.5 0 0 nsppol 1 nspden 2 spinat 0 0 0.000000 0 0 0.000000 0 0 2.000000 0 0 -2.000000 kptopt 1 ngkpt 1 3 3 nshiftk 1 shiftk 0.25 0 0 ecut 520 eV toldfe 4e-05 eV chksymbreak 0 chkprim 0FeO.files
FeO.in FeO.out none FeO tmp O.psp8 Fe.psp8Pseudopotentials
$ curl -O http://www.pseudo-dojo.org/pseudos/nc-sr-04_pbe_standard/O.psp8.gz $ gunzip O.psp8.gz $ curl -O http://www.pseudo-dojo.org/pseudos/nc-sr-04_pbe_standard/Fe.psp8.gz $ gunzip Fe.psp8.gz
$ abinit < FeO.files > FeO.log
Visualising the result
One can quickly check that an antiferromagnetic spin state has been produced.
$ c2x -vs --null FeO_DEN Rescaling spin from Bohr^-3 to A^-3 and calculating net spin Found 3D data for Spin min=-3.27618 max=3.27618 sum=-7.30971e-13 int=-1.07466e-15 int|s|=7.07998 (integral is e per cell for charge and spin densities)
The data contains signficant positive and negative values, and appears to have almost perfect inversion symmetry, in that (approximately) min=-max and sum=0. That the integral of the modulus of the spin is given as 7.08 implies a magnetic moment per Fe atom of 3.54μB, which is within the range of published values - a 2016 JCTC paper quotes an experimental range of 3.3 to 4.2μB, and a calculated range of 3.4 to 4.3μB.
$ c2x -vs -X='(8.664,0,0)(0,8.664,0)(0,0,8.664)' --xsf FeO_DEN FeO_spin.xsf
Here we have chosen to expand from the original four-atom cell to a unit cell which is itself cubic, in order to make the visualisation clearer. And whereas most of the images on this site are from XCrysDen, this time VESTA has been used.
The Fe atoms are gold, the O atoms small and red, and the isosurfaces of the spin density can be seen to be enclosing the Fe atoms, and that the Fe atoms are in layers of alternating sign of spin density, shown by the yellow and cyan colouring of the isosurfacs.