# [Pw_forum] 2D E(Kx,ky) data and contour plots using plot_2d

Tapas Dutta tdutta at iitk.ac.in
Sat Sep 17 10:35:25 CEST 2016

```I am trying to extract two-dimensional energy contour data (kx, ky, E) for
2D materials. For this, in the 'bands' calculation file, I am setting the 3
coordinates of the rectangle in terms of tpiba_c (in units of 2pi/a)*. *
And then using plot_2d in the bands.in file, I obtain the nicely tabulated
(kx, ky, E) data file for each band.
in the following two cases:

1. Orthogonal but unequal lattice vectors, e.g. phosphorene.
As the manual says, kx value are in units of (2pi/a). So I just need to
multiply by (2pi/a) to get actual values.
Are the yk values in units of 2pi/a too (as my input rectangle is in terms
of 2pi/a), OR are they in units of (2pi/b), in which case (a) I need to
multiply by (2pi/b) to get actual values, (b) scale by (a/b) to get scaled
coordinates in terms of (2pi/a) for contour plots?

2. Honeycomb lattice. e.g. graphene/silicene etc.
(a) What are the units of kx, ky?
(b) As the K_POINTS (in terms of tpiba_c) required in the 'bands'
calculation are vertices of a rectangle, the final values that plot_2d
generates, form a rectangle in kx-ky plane.
Is there a way to limit the data to the hexagonal 1st BZ as I need to
perform some operations limited to the 1st BZ?

Thank you.

Tapas
Department of Electrical Engineering,
Indian Institute of Technology, Kanpur
India - 208016
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