Molecular Dynamics Simulation Of Self-assembly Of A Nanotube From A Black Phosphorus Nanoribbon

As a typical two-dimensional material,currently,black phosphorus(BP)attracts much research attention due to its excellent electrical properties.Different from graphene which has its one-dimensional material,e.g.,nanotube,the BP nanotube has never been discovered or even fabricated in experiments.In the present study,molecular dynamics simulation is adopted to investigate the feasibility of fabricating a nanotube from a BP ribbon via self-assembly on a substrate from a carbon nanotube(CNT).In simulation,a rectangular BP ribbon with unsaturated edges is involved.According to the numerical results,two conclusions are drawn.(1)The self-assembly of a BP ribbon on a rotatable CNT at extremely low temperature(<50K)is studied.The effects of the chirality and radius of CNT,and temperature on the result of self-assembly of BP nanoribbon are demonstrated.Results indicate that a BP ribbon with perfect length can be attracted upon the CNT and finally formed into a BP nanotube at 8K.For the CNTs with the same radius but different chirality,the self-assembly of the same BP ribbon needs more time on a chiral CNT than on a zigzag or armchair CNT.As temperature is no less than 50K,the self-assembly fails even if the BP ribbon has perfect length.The reason is that the attraction of CNT to the BP ribbon becomes weaker at higher temperature.According to the numerical results,the prediction of obtaining a BP nanotube via self-assembly is verified.(2)In an experiment for fabricating the long rectangular BP ribbon,the surface of the BP ribbon(BP1)may attract some fragments,i.e.,BP1 is polluted.To investigate the feasibility of self-assembling a nanotube from the polluted BP ribbon,another BP ribbon(BP2)with much smaller sizes is chosen as a fragment,and the effect of the initially relative position of BP2 on the self-assembly is researched.When BP1 is between BP2 and CNT,the BP1 with perfect length can be successfully wound upon the CNT and finally formed into a nanotube.But the chirality of the new BP nanotube depends on the initial position of BP2 on the outer surface of BP1.A chiral BP nanotube may be obtained.If BP2 is between BP1 and CNT,self-assembly fails which is independent of the relative position of BP2 on the inner surface of BP1.Above numerical results is worthy of consideration in fabricating a BP nanotube in physical experiments.