MgO with atomic projections#
The files needed for this example are provided in the examples/MgO folder.
Often it is useful to know the various contributions of atoms in the structure to the electronic bands in the band structure, to analyse the chemistry and orbital interactions at play in the system. This can be computed for unfolded bands as well.
For a normal band structure calculation, the contributions can be inferred by colouring the band according to the elemental contributions, which can be done using sumo.
Similar plots can be generated for unfolded band structures. However, because the unfolded spectral function itself contains both the location of the band and its intensity, adding a third dimension of information (atomic projection) can be tricky to visualise.
In this example, we unfold the bands from a MgO 2x1x2 supercell with a Mg atom displaced to break symmetry. The procedure is essentially the same as described in the Si supercell example.
The only difference here is that we turn on the calculation of orbital projections in
LORBIT = 11 (
14 will also work) in the
INCAR file, and then use the
when plotting the unfolded band structure:
easyunfold unfold plot-projections --procar MgO_super/PROCAR --atoms="Mg,O" --combined --emin=-6 \ --emax=20 --intensity 6.5
Note that the path of the
PROCAR is passed along with the desired atom projections (
If the k-points have been split into multiple calculations (e.g. hybrid DFT band structures), the
should be passed multiple times to specify the path to each split
PROCAR file (i.e.
--procar calc1/PROCAR --procar cal2/PROCAR ...).
The atomic projections are not stored in the
easyunfold.json data file, so the
PROCAR file(s) should be kept for
replotting in the future.
--combined option creates a combined plot with different colour maps for each atomic grouping.
The spectral intensity is used to define the transparency (
alpha) allowing the fusion of multiple
projections into a single plot.
The default colour map for atom projections is red, green, blue and purple for the 1st, 2nd, 3rd and 4th atomic species
specified. This can be changed with the
--colours option, as well as several other plotting/visualisation settings –
see the output of
easyunfold unfold plot-projections --help for more details. If we wanted to plot the atomic
projections with the same colouring scheme as the
sumo plot above (i.e. red for Mg and blue for O), we can use:
easyunfold unfold plot-projections --procar MgO_super/PROCAR --atoms="Mg,O" --combined --emin=-6 \ --emax=20 --intensity 6.5 --colours "r,b"
In order to specify the atomic projections with
CONTCAR file for the supercell must be
present. If this is not the case, or we want to use projections from only specific atom subsets in the supercell, we can
alternatively use the
--atoms-idx tag. This takes a string of the form
f are integers corresponding to the atom indices in the VASP structure file (i.e.
PROCAR being used to obtain the projections). Different groups are separated by
can be used to define the range for each projected atom type. A comma-separated list can also be used instead of ranges
with hyphens. Note that 1-based indexing is used for atoms, matching the convention in VASP, which is then converted to
zero-based indexing internally in python. In this example, we could set
--atoms-idx="1-4|5-8" to get the same result
--atoms="Mg,O" (but without the figure legend).
In some cases, especially if there are many projection to be plotted at the same time, it can be clearer to create
separated plots for each. This is the default behaviour for
--combined is not specified.
easyunfold unfold plot-projections --procar MgO_super/PROCAR --atoms="Mg,O" --emin=-6 \ --emax=20 --intensity 6.5
There are many customisation options available for the plotting functions in
easyunfold plot -h or
easyunfold unfold plot-projections -h for more details!