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["D. R. Hamann" <drhamann@mat-simresearch.com>]

Dear Paola,

The response-function calculation of the elastic properties probably 
won't work for this case unless you are dealing with close-packed 
CNT's.  For isolated CNT's, you might get a correct number for the 
rigid-atom C_33 (assuming the tube axis is in the z direction).  The 
procedure for calculating the relaxed-atom quantities with anaddb, as in 
the tutorial, is unlikely to work.  The RF elastic and piezoelectric 
constant calculations are really designed only for continuous 3d solids. 

You could do finite-difference calculations with atomic relaxation, but 
these require extreme accuracy and force convergence to give correct values.

Don Hamann

paolajc@eden.rutgers.edu wrote:
> Dear all,
> Thank you very much for your previous feedback regarding the CNT structure.  I just have one question about using abinit to model carbon nanotubes.  Since these are 1D structures, is it possible to accurately obtain good results from abinit when modeling CNTs?  determining the total energy, elastic props, phonon dispersion,etc.  
>
> Thank you,
> Paola 
>
>   

--
D. R. Hamann
Mat-Sim Research LLC    | Deptartment of Physics
P.O. Box 742            |  and Astronomy
Murray Hill, NJ 07974   | Rutgers University
phone: 908-370-8079     | 732-445-4381

email: drhamann@mat-simresearch.com