Version 28 (modified by clarksm, 8 years ago) (diff)


Extended CNbands: Simulate E-k and DOS of CNTs and carbon nanoribbons

Welcome to the Extended CNbands development area. This project is for people actively developing source code and documentation for this tool.

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What is Extended CNbands?

Extended CNbands is a suite of FORTRAN and MATLAB/OCTAVE scripts that calculate the E-k relationship, density-of-states, and molecular structure for carbon nanotubes and carbon nanoribbons. It extends CNTbands in the following two ways:
(1) it treats sigma-pi hybridization using Extended Huckel Theory, and
(2) it simulates carbon nanoribbons.

Carbon Nanotubes
For simulations of carbon nanotubes, users may select between the Pz Orbital model, which uses the Zone Folding Method to treat the nanotube as a rolled up graphene sheet whose band structure is computed by a simple tight binding approach and assumes a single Pz orbital per carbon atom, or the more rigorous Huckel Theory Model, which treats the nanotube using four orbitals per carbon atom. Users indicate the carbon nanotube to be simulated by indicating the chirality vector (n,m), which uses the basis vectors for graphene. When using the Pz Orbital model, users may also indicate the tight binding energy and carbon-carbon spacing of the nanotube. In addition to plots of E-k, DOS, and molecular structure, the simulator also extracts some useful parameters from the input values and output plots, and displays these in an output log. Such outputs include diameter, number of hexagons per unit cell, and bandgap.

Carbon Nanoribbons
For simulations of carbon nanoribbons, currently only the Pz Orbital model is available. Users indicate the carbon nanoribbon to be simulated by indicating the chirality vector (n,m), which uses basis vectors that have magnitude equal to half those of graphene, and the relative origin of this vector, A or B type of atom in a unit cell. Users may only select carbon nanoribbons from the subset that can be described by setting this type of chirality vector, which is constrained in both magnitude and origin. In addition to plots of E-k, DOS, and molecular structure, the simulator also extracts the bandgap of the nanoribbon and writes it to the output log.

  1. Cerda and F. Soria, "Accurate and Transferable extended Huckel-type tight-binding parameters",
    Physical Review B, Volume 61, Number 12. March 15, 2000.

  2. Nakada, M. Fujita, G. Dresselhaus, M. Dresselhaus, "Edge state in graphene ribbons: Nanometer size effect and edge shape dependence",
    Physical Review B, Volume 54, Number 24, December 15, 1996.


Youngki Yoon, Diego Kienle, James Fodor, and Jing Guo

Last modified 05/23/2006 -- JKF

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