Exploring magnetic properties and Curved π-Conjugation of BxNyCz nanotubes using density functional theory

The aromaticity and magnetic properties of armchair (6,6) and zigzag (10,0) BxNyCz nanotubes (BNNTs) have been investigated by computing NICS values based on density functional theory. In addition, curved π-conjugation of selected NTs has been analyzed with π-orbital axis-vector (POAV) method. To evaluate magnetic property along the NT Z-axis, NICS values computed at several distance from NT center with a step size of 1 Å. In order to examine the effect of NT geometry as well as presence of Boron–Nitrogen atoms on magnetic properties, BxNyCz nanotubes with two different geometries including zigzag (10,0) and armchair (6,6) NT have been selected. Generally, the most magnetic property exhibited at the center of NTs and it tends to be reduced with increasing distance from center of NTs. Among of NTs investigated here, the zigzag CNT (10,0) exhibited the most central negative NICS value and therefore the most magnetic property. Instead BNNTs are the least deshielded ones. The calculated magnetic value presented very sensitive result to NT geometry. We attempted to explain overall resultant ring current – aromaticity – of NTs using strain energy of constituent hexagonals experienced by curvature of π-orbitals together with geometry of NT.

► The magnetic properties of NTs exhibit very sensitive result to their geometry.
► The zigzag CNT (10,0) exhibit the most aromatic property.
► Substitution C atoms with BN atoms and changing structure reduce aromatic property.
► The non-uniformity of POAV for adjacent atoms leads to misalignment of π-orbitals.
► The resultant π-conjugation system in CNT depends on alignment of hexagonals in CNT.