Ends Effect Of Boron Nanotubes And Simulation Of Cu/TaN Interface

With the rapid development of the computer and the progress of computing science,Computer simulation and design of the material has been widely used in research of material.Based on the first principle, we studied the following two parts: the port effect of boronnanotubes and structure simulation of Cu/TaN interface.1. Port effect of boron nanotubesBoron crystal has characteristics of low density, high melting point, super hardness andhigh chemical stability, etc. In recent years, theory predicts of boron nanotubes and highconductivity of one dimensional nanostructures inspire interest of people. So far, theresearches of one dimensional structures of boron nanotubes, nanowires, nanobelts andnanocones have been made considerable progress. People expect that, one dimensionalnanostructures of boron will become the core components of next generation nano device(such as high temperature semiconductor devices, mosfet, field emission and superconductingnano device, etc.)Based on the novel boron sheet of proposal of our group, in the paper we construct aseries of novel boron nanotubes which have different length and have hats on their two ends.The atom number of the boron nanotubes are60、80、100、120、140、160、180and the infinitenanotube has280boron atoms as its repeat unit. The "cap" of the port is a half of B60fullerenes which has "Football shape". In this paper, we calculated the energy, electronic statedensity, HOMO-LUMO gap value and average length of chemical bonds of structure. Theirstructure, stability and electrical properties are analyzed.The main results of this kind of novel boron nanotubes are as follows:1) The cohensiveenergy per atom in average decrease in a monotonous manner as the decrease of the length;2)Along with the increase of the length, the influence of the quantum size effect becomesweaking gradually. Their HOMO-LUMO Gap presents alternate decrease trend. The Gapvalue distributes between0.00eV and0.37eV. The infinite boron nanotube presentsmetallicity;3) s orbitals and p orbitals of this kind of boron nanotubes have obvious hybridcharacteristics.2. Structure simulation of Cu/TaN interface In this paper, based on the first principle and Chen–Mobius inversion, using the methodof atomistic level simulation we simulated and explored the body material of Cu, TaN andCu/TaN interface. We constructed two types of interface structures, corresponding to copperatoms on the top of tantalum atoms and copper atoms on the top of Nitrogen atoms. Wecalculated the energy curve of nanotubes using the first principle. We can get interatomicpotentials through inversion method of interatomic potentials put forward by our group.Finally, we implemented a detailed exploration of the structures, electronic properties anddislocations of the interfaces.The main results are as follows:1) The inversed potentials of Cu, TaN are self-consistent and effective which areextracted through inversion formula. Using the potentials we can reproduce theenergy curves which are calculated through the first principle. The relative error ofthe lattice constant of TaxNycalculated using pair potentials of pure elements andheterogeneous elements of TaN to experimental value is small.2) The different dislocation structures of Cu/TaN interface, with their crystal cell widthLcellare4,6,8,10,12and14, were respectively calculated. When the Lcellis a certainvalue, with the rise of the dislocation, the interface of the dislocation structureappeares discontinuous area and the discontinuous area gradually expands. When Pequals one, the interface appears vacancy and the vacancy expands to both sides as Pincreases. When P equals five, the vacancy disappears and the whole copper crystalstarts swirling upward until a copper atom squeeze out from the copper plane.3) Through comparing the two interface structures, we can find that the dislocationenergy of N terminated interface is lower than Ta terminated interface. Takentogether, the dislocation structure, with Lcell=8and P=0, is the most stable one.Through calculating the dislocation density of Cu/TaN interface, it can be found thatwhen the metal layer reaches a certain thickness, the interface should have arelatively stable dislocation structure.