# User-defined k-point lines

In the previous example, the k-point line is defined using conventional
high-symmetry point labels. This is not always practical, one may not
know the label of each high-symmetry point or use a different
convention. The keyword `kpoint.sympoints` therefore accepts
(fractional) k-point coordinates in place of labels. For example, in the
previous example, one could have used

``` shell
kpoint.sympoints = {[1/2 1/2 1/2],[0.0 0.0 0.0],[1/2 0.0 1/2],[1/2 1/4 3/4],[3/8 3/8 3/4]};
```

or even

``` shell
kpoint.sympoints = {'L',[0.0 0.0 0.0],'X',[1/2 1/4 3/4],'K'};
```

The RESCU plotting routine will show a `!` character for every tick mark
corresponding to a coordinate-defined checkpoint. You may fix the label
using the following command

``` shell
set(gca,'XTickLabel',{'L','G','X','W','K'});
```

The last argument should contain the label for all tick marks.

# Standard k-point lines

<figure>
<img src="figs/evsk_p.png" id="fig:evsk_p" alt="figs/evsk_p.png" />
<figcaption>Phosphorus band structure.</figcaption>
</figure>

In the previous example, the Bravais lattice is recognized to be a
face-centered cubic lattice (FCC). High symmetry k-point are labelled
conventionally; we follow [\[SC10\]](#SC10){.citation}, so user may turn
to it for additional details. Symmetric points and pre-defined lines
spanning irreducible Brillouin zone of most lattices have been
implemented. It is often not possible to follow a continuous line, and
hence most automatic lines consist of multiple segments. These can be
quite long, and hence the user should choose the number of k-points
accordingly. An example of an automatically generated k-line for
tetragonal bulk phosphorus is shown in `fig:evsk_p`{.interpreted-text
role="numref"}. Definitions and details are given in
`app:BS`{.interpreted-text role="ref"}.

::: {#citations}

[SC10]{#SC10 .citation-label}

:   Wahyu Setyawan and Stefano Curtarolo.
    `High-throughput electronic band structure calculations: Challenges and tools. <http://dx.doi.org/10.1016/j.commatsci.2010.05.010>`{.interpreted-text
    role="doi"} Computational Materials Science 49.2 (2010), pp. 299
    --312.
:::
