Mechanical properties of sp3-bonded carbon and boron nitride 2D membranes: A first principles study

Transverse compression and chemical passivation of few graphene or hexagonal boron nitride layers have been shown to be viable means to form ultrathin membranes rich in sp(3) bonds exhibiting intriguing mechanical behaviors. Here, density functional theory calculations are used to calculate second- and third-order elastic constants, as well as ideal breaking strengths of both layered and sp(3)-bonded arbon and boron nitride films. The sp(3)-bonded membranes consist of two or three planes of both existing and new in silico-designed bulk structures of carbon and boron nitride, and have either both, one, or none of the surfaces passivated with hydrogen. This study shows that carbon and boron nitride membranes rich in sp(3) bonds exhibit mechanical properties and ideal breaking strengths that compete with those of sp(2)-bonded layered films, and that there is a plethora of plausible stable structures of such sp(3)-bonded membranes, showing diverse electronic properties, and longitudinal and transverse mechanical behaviors. This study also suggests that by controlling thickness of the film and by tuning chemistry of the supporting substrate, transverse compression of layered carbon or hexagonal boron nitride films could lead to the formation of stable sp(3)-bonded 2D materials exposing clean surfaces, and therefore transferable, and exhibiting intriguing anisotropic mechanical and electronic properties.