Superlubricity in phosphorene identified by means of ab initio calculations

Phosphorene possesses a great potential for tribological applications due to its layered structure and for the capability of phosphorus to reduce friction and adhesion in steel-steel contacts. Here we present a comprehensive analysis of the static tribological properties of phosphorene based on first principles calculations. The most suitable exchange-correlation functional for describing the structural and electronic properties of multilayer phosphorene is carefully selected. The interlayer binding energy and shear strength are then calculated for two relative orientations of the layers. Layers stacked with the same orientation (armchair-armchair and zigzag-zigzag) are slippery as common solid lubricants, as MoS2 and graphite. While the armchair-zigzag orientation shows a remarkable superlubricity, with a reduction of one order of magnitude for the shear stress. We uncover the microscopic origin of such superlubric phase by analyzing the electronic charge at the layer interface.