[Pw_forum] Yet another question about graphene bandstructure

[Hadi Arefi]

Dear Julia,

I guess your K-path is not entirely coincides with the high symmetry points for graphene. Make sure you span the following routes with enough K:

0	0	0
0.666	0.333	0
0.5	0.5	0
0	0	0


HTH,

Hadi.
-----Original Message-----
From: pw_forum-bounces at pwscf.org [mailto:pw_forum-bounces at pwscf.org] On Behalf Of jbobak
Sent: 10 March 2014 17:04
To: pw_forum at pwscf.org
Subject: [Pw_forum] Yet another question about graphene bandstructure

Hi all,
I've searched the forum for this question, but nobody seems to be having quite the same issue, so I expect I'm doing something uniquely stupid. I am trying to calculate the band structure of graphene (using Espresso
5.0.3) for practice before I use a more complicated system. I do an SCF calculation with just the unit cell (2 atoms) with automatic k-points 18
18 1 0 0 0. Then I do a band structure calculation with k-points as
follows:

K_POINTS {tbipa}
7
0.00000 0.00000 0.00000 1
0.28868 0.16666 0.00000 1
0.57735 0.33333 0.00000 1
0.43301 0.41666 0.00000 1
0.28868 0.50000 0.00000 1
0.14435 0.25000 0.00000 1
0.00000 0.00000 0.00000 1

I then run bands.x, followed by plotband.x which I run interactively.
Everything works fine in that I get no errors, but the bandstructure plot is wrong (see attached pdf). The bands should cross at the K point. I think the problem has something to do with the k-points, which is why I have reproduced them above, but I have also attached the relevant input and output files. Could it be because the high-symmetry k-points I selected are not present in the automatically selected grid?

Thank you so much for any help,
Julia Bobak

Research Assistant
University of Victoria, Victoria, BC, CANADA