Edge reconstructions of hexagonal boron nitride nanoribbons: A first-principles study

highlights
• The armchair BNNR is the most stable edge structure, followed by the ac-48 edge.
• The zigzag-like ac-56 edge is more stable than the pristine zigzag structures.
• ac-677 and ac-678 type reconstructions are suggested as possible edges in BNNR.
• The zz-57 reconstruction in hetero-elemental BNNR is different from that in GNR.

The edge reconstructions of hexagonal boron nitride nanoribbons (BNNRs) and their stabilities have been investigated by the first-principles calculations of both their binding and edge energies. It is found from our calculations that the binding energy we have used is a reliable and useful quantity for judging the stabilities of different edge reconstructions of the hetero-elemental BNNRs instead of the conventional edge energy one, especially for those BNNR's edges with unequal number of B and N atoms. In addition, other four main results have been obtained: (1) the armchair BNNR is the most stable edge structure and the characteristic ac-48 edge reconstruction for the BNNRs is predicted to be the second most stable edge in all the discussed BNNR edge structures. But, its zigzag edge is less stable. (2) The zigzag-like ac-56 type reconstructions are more stable than the pristine zigzag structures, which is different from that of the graphene nanoribbon (GNR), being less stable than the zigzag GNR. (3) The stabilities of BNNR's ac-677 and ac-678 type edge reconstructions lie between its ac-56-B and zz-57-B edges. (4) The zz-57-B(-N) edge reconstruction lowers the edge energy by a small quantity, which is also different from that of GNR. Moreover, the zz-57-B edge structure is more stable than the zz-57-N one, indicating that B-rich edge is easier to be reconstructed while the N-rich edge is more stable. Our theoretical calculations suggest the many possible reconstructed edge structures for the bare BNNRs, which is important for BNNR's application in future nanoelectronics and spintronics.