Interaction between layers of the multi-wall carbon nanotubes

We show that the symmetry of the layers of the multi-wall tubes strongly affects the inter-wall interaction. The total symmetry of the tubes is highly reduced with respect to the high symmetry of the isolated layers, and this results in low interaction which decreases with the symmetry breaking rate. The strongest interaction is found for the commensurate tubes with achiral walls. On the other side, the tubes with chiral walls interact negligibly. The results are used for detailed tribological study: various new phenomena are found and the tubes with maximal friction are selected.