Multiscale computations for carbon nanotubes based on a hybrid QM/QC (quantum mechanical and quasicontinuum) approach
J. Y. Park, C. H. Park, J. S. Park, K. J. Kong, H. Chang and S. Im
Journal of the Mechanics and Physics of Solids, 58, 86-102 (2010).

ABSTRACT
An effective multiscale computing scheme based on QM/QC (quantum
mechanics/quasicontinuum) is applied for simulation of Carbon nanotubes (CNTS)
mechanics. First, quasicontinuum simulation of deformations of curved
crystalline structures is conducted to examine the fully nonlocal behavior of
CNTs with the aid of high-order interpolation functions and the "cluster"
concept, which facilitates accurate energy approximation for crystals. Next, a
multiscale computing approach based on QM/QC hybridization is devised, and
applied for simulation of CNT mechanics. The bonding configuration changes, e.g.
bond breaking or creation, near defect sites are correctly represented with the
QM/QC hybrid model. For studying electronic proper-ties coupled with the
mechanical deformation of CNTs, the change of the electrical properties from an
initial semiconductor into metal under mechanical bending is investigated.
Single-walled CNTs having various types of defects and subjected to uniaxial
tension are considered for fracture. The theoretical strength of the CNTs in the
presence of each defect is computed based on the QM/QC hybrid scheme, wherein
the defect neighborhood is modeled as a QM zone for a first-principle-based
calculation using density functional theory (DFT), and the remaining area as a
QC zone. This multiscale computing approach greatly improves the accuracy in the
prediction of the failure strains of CNTs over a purely molecular mechanical or
quasicontinuum method.