[Pw_forum] Strange bandstructure for metallic carbon nanotube

[chengyu yang]

Hi everybody.
      Sorry to post this email again cause the image in this one is bigger
and easy to see.
      I tried to plot the bandstructure for carbon nanotube(5,5), however,
the result looks strange. I have 20 carbon atoms in a unitcell, and I set
the number of bands(nbnd=80 or 48).
     nbnd=80 is out of the consideration that conduction bands+valence
bands.
<http://imageshack.us/photo/my-images/51/cnt55bands80.jpg/>

http://imageshack.us/photo/my-images/36/cnt55bands80.jpg/
    nbnd=48 is from the 20% more for metal.(here the carbon nanotube is
metallic)

<http://imageshack.us/photo/my-images/202/cnt55bands48.jpg/>
http://imageshack.us/photo/my-images/163/cnt55bands48.jpg/

    The third picture is after I added no_overlap=.true. in the
bands.infile for nbnd =48.
http://imageshack.us/photo/my-images/850/cnt55bands48nooverlap.jpg/

    All the three pictures are far from the band structure in literature,
and I don't know if they are wrong.
    Can somebody give me an advice and I apprieciate it very much.
    Thank you!

    Best regards.

Chengyu Yang
MMAE
University of Central Florida, USA
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