First Principle Study On Electronic Structure,Magnetism And Optical Properties Of Modified Graphene Nanoribbons And PC₆ Nanoribbons

Nanoribbons,a kind of quasi-one-dimensional ribbon structure of nanomaterials,have excellent electronic properties and optical properties,and produce peculiar quantum confinement effects and piezoelectric phenomena.Nanoribbons can be widely used in the field of nanoelectronics.In this paper,by using first-principles calculation method based on density functional theory,the effects of Ti atoms on different positions and different doping concentrations on the electronic,magnetic and optical properties of graphene nanoribbons have been systematically studied.The structure and electronic properties of pure PC6 nanoribbons and the effects of N and B single and diatomic doping on the electronic and optical properties of PC6 nanoribbons are studied in detail.The main conclusions obtained are as follows:(1)The effects of Ti atoms at different positions and different doping concentrations on the electronic,magnetic and optical properties of zigzag and armchair graphene nanoribbons have been systematically studied.The results show that:regardless of the doping position,ZGNR(4,5)doped with a single Ti atom will change from the AFM state to the FM state.Due to the increase of the Ti doping concentration,the edge state of the system gradually deteriorates.Ti doping will cause spin suppression in the nearby area and the spin polarization distribution is almost localized Ti atoms at higher doping concentrations.The introduction of Ti atoms cannot change the original semiconducting of AGNR(7,4),but its band gap can be adjusted by changing doping position and doping concentration.The band gap decreases with the increase of Ti doping concentration,and the dispersion of LUCB and HOVB gradually increases,LUCB and HOVB are mainly due to the contribution of the charge of Ti atoms and adjacent C atoms.In the ultraviolet range of 4?9 eV,Ti doped AGNR(7,4)and ZGNR(4,5)can absorb light of a specific wavelength and the absorption intensity can be effectively adjusted by changing the doping concentration.(2)The structure and electronic properties of pure PC6 nanoribbons and the effects of N and B single and diatom doping on the electronic and optical properties of PC6 nanoribbons were studied in detail.The results show that pure 4-ZPC6NR is semiconducting with a band gap of 0.23eV.No matter monoatomic or diatomic doping,N doping makes 4-ZPC6NR change from semiconducting to metallic,while B doping reduce the band gap.The pure 5-APC6NR is semiconducting and when 5-APC6NR is substituted by N or B atoms,it can cause a change in band gap.The introduction of N or B atoms can effectively adjust the absorption intensity of 4-ZPC6NR and 5-APC6NR in a specific frequency range.