Theoretical Study On The Structural Design And The Properties Of Several Carbon-Based Materials

Carbon,as one of the most important basic elements on earth,has a wide variety of carbon allotropes due to its varied and unique bonding patterns.Several well-known carbon materials,such as graphite and diamond,possess excellent properties irreplaceable by other elemental materials,so carbon-based materials have always been the focus of theoretical and experimental research.With the continuous improvement of theoretical calculation methods and the gradual improvement of computing resources,it has become a common method to design and study new materials by using theoretical simulation.In this paper,the first-principles calculation based on the density functional theory is adopted to study the properties of several carbon-based materials in detail.The specific contents are as follows:1.A new carbon allotrope bct-C5 was predicted in a tetragonal system.Bct-C5 was an indirect band gap semiconductor with a band gap of 3.17 eV.The Vickers hardness of bct-C5 was calculated to be 31.6 GPa,and the shear strength was up to 55.9 GPa.The simulated x-ray diffraction pattern was agreement with the experimental data of the detonation and chimney soot.These results indicate that bct-C5 can be successfully prepared in the near future and has potential applications in mechanical and electronic devices.2.A new allotrope composed of sp-and sp3-hybridized bonds was predicted,called TD-carbon.TD-carbon is a semiconductor with a direct band gap of 2.82 eV and a low density of 0.673 g/cm3.It absorbs visible light more easily than TiO2.These results suggest that TD-carbon is a potential functional material for energy storage,electronics,optics,and optoelectronics.3.The threshold displacement energy of T-carbon and cascade collision processes,as well as the effects of typical defects induced by collision on its electronic properties were investigated.It was found that the displacement threshold energy was anisotropic in T-carbon.The band gap of T-carbon could be tuned effectively by irradiation,and the mechanism was expounded by analyzing the band structures and band decomposed charge density.These results play important guiding roles in further understanding T-carbon,exploring the irradiation resistance of T-carbon and revealing the formation mechanism of irradiation defects,thus providing a theoretical basis for the application of T-carbon in radiation environment.4.The effects of boron/nitrogen dopant on the geometry,electronic structure and magnetic properties of the penta-graphene system were investigated.It was found that the electronic band gap of penta-graphene could be tuned and varied between 1.88 and 2.12 eV depending on the type and location of the substitution.The introduction of dopant could cause spin polarization and lead to the emergence of local magnetic moments.The main origin of the magnetic moment was analyzed and discussed by the examination of the spin-polarized charge density.These results provide the possibility of modifying penta-graphene by doping,making it suitable for future applications in the field of optoelectronic and magnetic devices.Figure[27]table[3]reference[114]...