  In recent years, graphene-like boron carbide and carbon nitride nanosheets
have attracted remarkable attentions, owing to their semiconducting electronic
nature and outstanding mechanical and heat transport properties. Graphene-like
BC6N is an experimentally realized layered material and most recently has been
the focus of numerous theoretical studies. Interestingly, the most stable form
of BC6N monolayer remains unexplored and limited information are known
concerning its intrinsic physical properties. Herein, on the basis of density
functional theory (DFT) calculations we confirm that the most stable form of
BC6N nanosheet shows a rectangular unitcell, in accordance with an overlooked
experimental finding. We found that BC6N monolayer is a semiconductor with 1.19
eV direct gap and yields anisotropic and excellent absorption of visible light.
First-principles results highlight that BC6N nanosheet exhibits anisotropic and
ultrahigh tensile strength and lattice thermal conductivity, outperforming all
other fabricated 2D semiconductors. We moreover develop classical molecular
dynamic models for the evaluation of heat transport and mechanical properties
of BC6N nanomembranes. The presented results in this work not only shed light
on the most stable configuration of BC6N nanosheet, but also confirm its
outstandingly appealing electronic, optical, heat conduction and mechanical
properties, extremely motivating for further theoretical and experimental
endeavors.
