Computer simulation of nanotube contact

We develop procedures of numerical solution of nanostructure contact problems, which are based on the time discretization of nonlinear equations of molecular mechanics. The matrices and vectors of these equations are determined by using the Morse law of covalent atomic interaction, the fictitious rod elements to take account of angular variations between neighboring atomic covalent bonds, and noncovalent Van der Waals forces to take account of contact interactions between the graphene-like nanostructures. The procedures developed were included into the computational package PIONER, which was used to solve the problem of contact/self-contact of two nanotubes under conditions of dynamic equilibrium. We showed that the type of contact interaction significantly depends on the impact velocity of nanotubes. For a relatively small impact velocity, the nanotubes "adhere" to each other with a small deformation of their walls, due to the action of the Van der Waals attractive forces. As the impact velocity increases, the nanotubes fly apart because of the action of noncovalent repulsive forces. As the impact velocity continues to increase, there is a strong deformation of nanotubes with instantaneous "adhesion" of opposite ends and further separation of tubes. We show that taking account of the noncovalent forces of interaction between the opposite parts of the nanotube walls prevents their self-intersection; in this region of the nanotube contact, ovalization of their transverse cross-sections occurs.