Understanding Faceting in Boron-Nitride and Carbon Nanotubes

Graphite and hexagonal boron nitride (h-BN) are known to share many structural characteristics such as interlayer spacing and bond length, in spite of their completely different atomic bond types, nonpolar homonuclear and strongly polar, respectively. Only recently, a connection of static polarizability and bond polarity with the interlayer spacing and stacking energetics in the two materials has been elucidated [1]. Yet, in the case of curved sheets forming a nanotube (NT), the presence of angular strain and non-uniform stacking between the layers give rise to complex force patterns that subtly differ in the two cases. , by means of classical MD simulations of h-BN and carbon NTs we reveal how the interplay between angular strain and lateral interlayer forces enable the formation of facets in the two materials. The role of the curvature (NT size) and of chirality is discussed along with the important consequences of faceting in the static and frictional properties of multiwall NTs. [1] O. Hod, J. Chem. Theory Comput. 2012, 8, 1360$-$1369