Bistability of multiwalled carbon nanotubes arranged on plane substrates

Stationary states of multi-walled carbon nanotubes have been studied. The numerical simulation showed that nanotubes become bistable systems at rather large diameters. They can be in two stable states in spite of the interaction with substrates: in an open state with a hollow internal cavity and in a collapsed state. The interaction with a plane substrate leads to the nanotube flattening, making its transition to a collapsed state more energetically preferable (the stronger the interaction, the more preferable is the transition). It is shown that a change in the multilayer nanotube shape due to its interaction with the substrate or due to its collapse leads to a sharp increase in the number of its collective eigenmodes, in which all its layers take part. The energy profile of the transition is found between the steady states of the nanotube; the profile is a strongly asymmetric double-well potential with the first narrow minimum, which corresponds to the collapsed state and the second broad minimum, which corresponds to the nanotube open state.