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[Matthieu Verstraete <mjv500@york.ac.uk>]

Yes, but the supercell you place them in has to be big enough (as always).
This can have very subtle effects, in particular if you choose supercells 
which do not have the same symmetry as the CNT.

See "Room Temperature Peierls Distortion in Small Diameter Nanotubes" 
Phys. Rev. Lett. 94, 015503 (2005) for an example (not only abinit was 
used): the 5-axis of a 5,0 is impossible in a 3D supercell, and the 
effects can be devastating for small energy differences (in the sense that 
very very large cells are needed). The effect they were looking for was 
precisely a symmetry-breaking Peierls distorsion.

Carbon ecut also has to be fairly high (more towards 40 Ha than towards 
the 20-25 Ha you sometimes see in the literature). Check out the PAW 
potentials for this. Some are very efficient (down to 15 Ha). But no 
linear response yet.

Phonons, structures, etc... have all been done.

Have fun

Matthieu

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Dr. Matthieu Verstraete                 mailto:mjv500@york.ac.uk
Dept. of Physics, University of York,     tel: +44 1904 43 22 08
Heslington, YO10 5DD York, United Kingdom fax: +44 1904 43 22 14