Computational Design And Physical Properties Of Two Kinds Of Carbon Nanomaterials

Diversity of chemical bonds of carbon elements(sp1,sp2,sp3)enables them to form abundant allotropes,and the rich properties of abundant allotropes make carbon materials widely used in life.Therefore,the research on carbon has been a hot topic in the filed of condensed matter and material physics.At the same time,with the development of computational physics,theoretical prediction has become an effective way to study material science.Based on the first-principles method of density functional theory(DFT),this paper designs new carbon heterogeneous phases by means of assembly and calculates their related physical properties.Using C16 cage-like clusters as assembly motifs,a novel heterogeneous phase(T-C56)of 3D low-density carbon was designed.The calculated results show that the new carbon phase T-C56 shows good stability in terms of energy,kinetics,thermodynamics and mechanics,and is more stable than the T-carbon and C20-sc carbon experimentally.Notably,although the T-C56 is low density carbon phase(2.72 g/cm3),it exhibits superhard properties with a Vickers hardness of 48.71 GPa.At the same time,the calculation of Young's modulus and ideal strength shows T-C56 mechanical anisotropy.Specifically,after computational analysis of electrical and optical properties,T-C56 are transparent indirect semiconductors with a band gap of 3.18 eV(HSE06).Above,it can be seen that T-C56 as a unique carbon hetero structure phase is expected to have broad application prospects in optical and aerospace equipment due to its lightweight,transparent and superhard characteristics.Furthermore,we have studied two carbon chains of the experimental synthesis of two compounds after dehydrogenation to obtain a new two-dimensional Dirac semi-metallic carbon phase spalgraphene through assembly.After calculation,its energy stability performance is good,and kinetics,thermodynamics(>1800K),mechanics also meet the stability conditions.The calculated surface of electronic properties its two energy bands located near the fermi level form closed dirac cones near the C0 in the first brillouin zone.there are quasi-dirac cones(Eg=18 meV)in the G-?0 section,and the anisotropy is very strong:when ?=180° the maximal Fermi velocity reaches 8.69×105 m/s,and the smallest Fermi velocity is 7.75×104 m/s when the cp=49°.While in the range-1.51 eV?-1.87 eV of energy windows that move down the fermi level,the continuous distribution of dirac points appears one-dimensional nodal line.And removal of spalgraphene vacuum layer can form stable three-dimensional crystal spalgraphene-3D.Therefore,this novel carbon phase is expected to be promising for nanodevice applications.