A First-principles Study Of Two-dimensional BC₂N Magnetic Modulation

The structure of two-dimensional BC₂N is stable.Because it has a two-dimensional geometric structure similar to single-layer graphene,its electronic properties combine the excellent physical and chemical properties of single-layer graphene and two-dimensional hexagonal boron nitride.But unlike graphene with zero band gap,two-dimensional BC₂N has a suitable band gap,which makes it an important role in the field of electronics.Pure two-dimensional BC₂N is a non-magnetic nanomaterial,because of the lack of magnetism makes it difficult to apply to the field of electromagnetics.Therefore,it is particularly important to inject magnetism into the two-dimensional BC₂N,which can improve its performance and expand the application range.Many theories show that two-dimensional BC₂N can introduce magnetism through modulation and change its electronic properties.Modulation methods mainly include defects,adsorption,doping,applying internal stress,and directly applying external electric field.Among them,the effective and common modulation methods are mainly defect modulation and adsorption modulation.Based on the first-principles calculation method of density functional theory,this paper first discusses in detail the modulation effect of four single atomic vacancy defects(V_N,V_C1,V_C2,V_B)on two-dimensional BC₂N,mainly studies the geometric structure of the modulation structure,Magnetic properties and their electronic properties.The results show that four single-vacancy defect systems can exist stably.N,C1 atomic single vacancy defects(V_N,V_C1)show no magnetism,and V_C2,V_Bdefect systems show magnetism.At the same time,the introduction of single vacancy defects will also change the properties of the two-dimensional BC₂N:For the V_Nand V_C1defect systems,a single vacancy defect narrows the band gap of the two-dimensional BC₂N;the V_C2defect system shows metallic properties;the V_Bdefect system exhibits half Metal nature.Through the analysis of the magnetic and electronic properties of the defect system,it is concluded that the magnetism of the defect system(V_C2,V_B)mainly comes from the atoms around the defect,because the generation of defects affects the electron rearrangement of the atoms around the defect.The study of the vacancy defects of the two-dimensional BC₂N provides a theoretical basis for its application in the field of electromagnetics,and contributes to the modulation research of the magnetic aspects of the two-dimensional BC₂N with vacancies.The properties of 3D transition metal atom(TM)adsorption modulation of two-dimensional BC₂N are also studied.The geometric structure,magnetic properties and electronic structure of the modulated two-dimensional BC₂N are mainly discussed.The results show that the transition metal atoms(V,Cr,Mn,Fe,Co,Ni)can be stably adsorbed on the two-dimensional BC₂N,and the V,Cr and Mn atoms obviously tend to be stably adsorbed on the BC₂N hole(H).The other 3d transition metal atoms(Fe,Co,Ni)tend to be adsorbed stably on the C atom(Tc).It can be known from the adsorption energy that Cr and Mn are physically adsorbed on the single layer BC₂N,and the transition metal atoms(V,Mn,Fe,Co,Ni)are chemically adsorbed on the single layer BC₂N.Magnetic properties indicate that other transition metal atom adsorption systems besides Ni adsorption system can introduce magnetism,and the magnetic moment of the adsorption system is mainly concentrated on the transition metal atoms.The introduction of 3d transition metal atoms(V,Cr,Mn,Fe,Co)leads to spin polarization in the adsorption system,and the spin polarization rate reaches 100%(Half-metallic properties),which has the characteristics of spintronic materials.In addition,the influence of Hubbard U value on the magnetic(V,Cr,Mn,Fe,Co)adsorption system is also considered.When U=0,it can be seen from the Fermi level state density map that all five adsorption systems are semi-metallic.With the increase of U,the semi-metallic properties of the Fe and Cr atomic adsorption system disappear,and the system can change from semi-metallic to metallic.