Study On Stability And Electronic Structure Of ZrB₃ And ZrB₄ Two-dimensional Structures

As an important chemical raw material,boron is widely used in chemical industry,nuclear industry,aerospace and all kinds of fields.Boron,a two-dimensional material similar to graphene,was successfully prepared exprimentally in 2015.Which initiated a new era of boron 2-d material research.Boron is a two-dimensional material with thickness of mono-atom layer that composed of boron atoms,which has the rich chemical and physical properties.In recent years,people attempt to introduce metal atoms into the two-dimensional system of boron,and many novel quantum effects have been obtained.Such as Dirac electron state,the property of semi-conductivity,etc.In this paper,we present two kinds of stable zirconium boride two-dimensional monolayer lamellar structures,and analyze the property of stability,electronic and bonding orbital properties of these two monolayer structures by using the method of first principles based on density functional theory.The results of research are as follows:?1?Zr,B ratio of 1:4 zirconium boride two-dimensional structure has been widely investigaed,a stable two-dimensional ZrB₄ monolayer sheet structure was obtained,which can be seen as a hexagon composed of three ZrB₄ unit cells expands,The analysis of phonon spectrum and the simulation of molecular dynamics show that the structure has good stability.By analyzing the differential charge density and natural bonding orbital,it can be seen that the4d orbital of Zr and sp² of B hybridization are the key to the stability of two-dimensional ZrB₄.The calculation of electronic properties indicates that this kind of two-dimensional ZrB₄structure has metallic properties so it is a conductor.?2?Based on the algorithm of particle swarm optimization,we obtained a stable two-dimensional ZrB₃ monolayer lamellar structure with a chemical ratio of 1:3 between Zr atom and B atom.This structure can be regarded as composed of two kinds of different hexagons,a complete ZrB₃ planar structure can be formed by the extended arrangement of these two hexagons.Analysis of frequency and molecular dynamics simulation show that the structure has good property of dynamic and thermodynamic stability.It can be found that the stability of the structure is mainly due to the hybridization contribution of the 4d orbital of Zr atom and the 2p orbital of B atom by analysing figure of the DOS and molecular orbital theory.The calculation of electronic properties shows that the two-dimensional plane structure ZrB₃ has metal properties.