Theoretical Prediction And Properties Simulation Of Some Two-dimensional Materials

Non-layered two-dimensional structures with the atomic thickness recently attract much attention.In this paper,based on density functional theory,we use first principles to predict and simulate the properties of some two-dimensional materials.We have done two main tasks.In the first part of our work,we predicated a two-dimensional structure of non-layered ScC,denoted as ScC sheet,and evaluated its potential as the electrode material of Na-ion battery.The stability of ScC sheet is determined by the cohesive energy,phonon spectrum and potential energy curve calculations.Interestingly,the proposed ScC sheet can exhibit many unexpected electrochemical properties.It is found that ScC sheet can possess strong Na adsorption capability.Both pristine and Na-interacted ScC sheets represent good electronic conductivity due to the metallic nature.The structural degradation of the ScC during the sodiation and desodiation processes are not anticipated.Besides,our results reveal that the ScC sheet has a minimal diffusion barrier of 9 meV and the calculated theoretical capacity of ScC sheet can reach to 940 mAhg^-1 on the basic of the second layer adsorption.Thus,benefiting from these features,ScC sheet is expectable to be served as a promising electrode material for the Na-ion battery.In the second part of our work,via density functional theory（DFT）computations we identified four non-layered wide band-gaped 2D structures,including MgO,CaO,CaTe and BaSe sheets.High dynamic and thermal stabilities are confirmed by the phonon spectra and the potential energy curves calculations,respectively.The feasibilities of the achievements of these 2D structures are proved by comparing the formation energies of them with that of experimentally fabricated silicene and germanene.Intriguingly,comparing with the indirect band-gaps of the bulk structures,we found these 2D structures exhibit a direct band-gap character.Moreover,the proposed MgO,CaO,CaTe and BaSe sheets possess the band-gaps of 4.89,3.61,2.81 and 2.96 eV,respectively.Our results,to a certain extent,pave the way for the applications of 2D structures to the photoresponse devices with the short wavelengths.