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You have to give an explicit path after the `INPUT_THERMO`
namelist (see `what='scf_bands'` and `what='scf_2d_bands'`).
There are two possibilities to specify a path in the Brillouin zone.
You can use explicit coordinates of the first and last points of
each line (in cartesian or crystal coordinates) and a weight that indicates
the number of points in the line, or you can use labels to
indicate the first and/or the last points. The available labels depend on
the Brillouin zone and are illustrated in the file
`Doc/brillouin_zones.pdf` in the main QE documentation.
Labels for points given by explicit coordinates can be added after
the weights.
Usually, the same label that indicates the coordinates of the point
is written in the dispersion plot, but it is also possible
to override this label, adding a letter after the weight as for
the points given by explicit coordinates.
Note that labels are given without quotes, while the additional letter
after the weight must be written between single quotes.
An example of a path for the fcc lattice:
7
gG 20
X 20
W 20 'gS1'
1.0 1.0 0.0 20 'X'
gG 0
gG 20
L 0

This path has five lines, the first from
1#1
to
*X*
with
20
points,
the second from
*X*
to
*W*
(that in the plot will have the label
2#2
)
with 20 points, the third from
*W*
to the point of coordinates
(1.0, 1.0, 0.0)
(that in the plot will have the label
*X*
), the fourth from
(1.0, 1.0, 0.0)
to
1#1
with
20
points and a final line from
1#1
to
*L*
with
20
points.
Until version `1.8.1` labels are read as three characters, so it
is important not to write the weights too close to the labels.
Grüneisen parameters are not analytic at the
1#1
point so to obtain a correct plot, the
1#1
label in the middle of a
plot must be repeated twice, as in the example.

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2024-02-14