Ascalaph  suite
for Molecular Mechanics simulations

Dear. Collegue

Thanks to Marino, I have found the reason for the difference in our bending stiffness calculation. The original discussion is here:
http://imechanica.org/node/4029

The reason why we have a higher bending stiffness is due to the dihedral term. This dihedral term does have a significant contribution to the bending stiffness. However, in Ref. [26], apparently, this dihedral term was ignored.
I have written a short document showing the contribution of the dihedral term to the bending stiffness. Please take a look at the attachment.
I received great help from Dr. Huang and Marino. Thank you very much.

Qiang Lu and Rui Huang

Department of Aerospace Engineering and Engineering mechanics, University of Texas, Austin,
TX 78712, USA

(PRB,74,245428,2006)  Based on a molecular mechanics concept, a nonlinear stick-spiral model is developed to investigate the mechanical behavior of single walled carbon nanotubes (SWCNTs). The model is capable of predicting not only the initial elastic properties (e.g., Young’s modulus) but also the stress-strain relations of a SWCNT under axial, radial, and torsion conditions. The elastic properties, ultimate stress, and failure strain under various loading conditions are discussed and special attentions have been paid to the effects of the tube chirality and tube size. Some unique mechanical behaviors of chiral SWCNTs, such as axial strain-induced torsion, circumferential strain-induced torsion, and shear strain-induced extension are also studied. The predicted results from the present model are in good agreement with existing data, but very little computational cost is needed to yield them.