二维单层MoSi_(2)X_(4)(X=N,P,As)的电子结构及光学性质研究

Study on the Electronic Structure and Optical Properties of Two-dimensional Monolayer MoSi_(2)X_(4)(X=N,P,As)

采用平面波超软赝势方法研究了二维单层 MoSi_(2)X_(4) (X=N,P,As)的稳定性、电子结构和光学性质.研究结果显示,基于单层 MoSi_(2)N_(4)的两种同分异构体 M1 和 M2 所构建的六种晶体结构具有较好的动力学稳定性.通过能带和有效质量的计算,单层MoSi_(2)N_(4)在 MoSi_(2)X_(4) (X=N,P,As)六种晶体结构中显示出最宽的间接带隙和最高的载流子迁移率.随后带边电位的计算结果表明,单层 MoSi_(2)N_(4)带边势分别为 M1:-0.368、1.416 V,M2:-0.227、1.837 V,其结果相较于MoSi_(2)P_(4)和 MoSi_(2)As_(4)导带边电位更负,价带边电位更正,是六种晶体结构中最适合用作光催化剂的材料.同时,光吸收谱的计算结果显示,单层 MoSi_(2)N_(4)的光学吸收表现出明显的各向异性,在可见光和紫外光波段内具有较强的光吸收能力,说明其在可见光催化领域有着潜在的应用前景.这些结果为进一步深入研究二维单层 MoSi_(2)N_(4)在光催化水解领域的应用提供了理论指导.

Two-dimensional systems have served as potential materials in the generation of clean energy and energy storage,which are attributed to their particular advantages in photovoltaic,photocatalytic and electrochemical fields.Recently,the two-dimensional monolayer MoSi_(2)N_(4) has been successfully fabricated.Motivated by these recent experimental results,herein the structural stability,electronic structures and optical properties of monolayer MoSi_(2)X_(4) (X=N,P,As) using the method of plane-wave ultrasoft pseudopotentials were investigated.Six crystal structures were constructed based on the monolayer MoSi_(2)N_(4) isomers M1 and M2.The phonon spectra did not show negative frequency vibration mode in the entire Brillouin region,indicating good dynamic stability.By analyzing the density of states,it can be known that the top of the valence band and the bottom of the conduction band of the six crystal structures are mainly contributed by MoX_(2) (X=N,P,As) orbitals.Energy band structures and effective masses show that the monolayer MoSi_(2)N_(4) exhibits the widest indirect band gap and the highest carrier mobility among the six crystal structures.The band edge potentials show that the monolayer MoSi_(2)N_(4) band edge potentials are M1:-0.368,1.416 V and M2:-0.227,1.837 V,respectively.Compared with MoSi_(2)P_(4) and MoSi_(2)As_(4),the monolayer MoSi_(2)N_(4) has a more negative potential of the conduction band edge and a more positive potential of the valence band edge,indicating that it is the most suitable material for photocatalysts among the six crystal structures.Meanwhile,the optical absorption spectrum shows that the optical absorption of monolayer MoSi_(2)N_(4) exhibits excellent optical absorption ability in visible and ultraviolet wavelengths,indicating that it has a potential application prospect in the field of visible photocatalysis.The results provide theoretical guidance on the application of monolayer MoSi_(2)N_(4),for further research in the field of photocatalytic hydrolysis.