[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.
Now can someone please help me find the actual (unscaled) values of kx, ky
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.

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