A First Principle Study Of Electronic And Mechanical Properties Of TMDs/Ti₃C₂X₂ （X=S,Se,Cl,Br） Heterostructures

The stacking of Ti₃C₂ with transition metal dihalide（TMDs）materials is an effective strategy to improve the physical properties of single material,and how to tune the related properties of these TMDs/Ti₃C₂ heterostructures is also an important scientific problem.Before that,the electrochemical properties of TMDs/Ti₃C₂heterostructures have been studied by researchers.However,the impact of external field coupling with novel functional groups（S,Se,Cl,Br）on their physical properties is rarely mentioned.Therefore,we systematically studied the effects of external fields and novel functional groups on the structural,electronic,and mechanical properties of TMDs/Ti₃C₂ heterostructures.The main research of this article is as follows:（1）Systematic investigated the structural and electronic properties of TMDs/Ti₃C₂ heterostructures and TMDs/Ti₃C₂ Janus.Covalent bonding between the Mo S₂/Ti₃C₂ layers was found by the bond populations and Mulliken charge,Charge transfer from Ti₃C₂ to Mo S₂,and the bonding of Mo Se₂/Ti₃C₂ is a combination of covalent and ionic bonds.We find that the lattice parameters and bond lengths of the TMDs/Ti₃C₂ Janus appear to be inflated,and transition of Mo S₂ from semiconductor to metal in Mo S₂/Ti₃C₂SCl.（2）Investigated separately the effects of external fields and functional groups（S,Se,Cl,Br）on the structural and electronic properties of TMDs/Ti₃C₂ heterostructures.We found that stretching enhances the carrier mobility of TMDs/Ti₃C₂ and compression decreases the carrier mobility.The functional groups weaken the interlayer electronic coupling between TMDs and Ti₃C₂,leading to an increase in the lattice parameters and interlayer distance of TMDs/Ti₃C₂X₂.The strain further increases the layer spacing of TMDs/Ti₃C₂X₂;and induces TMDs to exhibit metallic properties.The conduction band edge（CBE）and valence band edge（VBE）of TMDs/Ti₃C₂X₂ were found to vary linearly under the electric field effect.（3）Combine the first-principles with the theory of continuum mechanics to calculate the mechanical parameters such as elastic modulus,ultimate strength and stress-strain curves for TMDs,Ti₃C₂X₂ and TMDs/Ti₃C₂X₂（X=Br,Se,Cl,S）.Functional groups were found to not only reduce the elastic modulus and strength limit of the heterostructures and each monolayer,but also increase the Poisson’s ratio of the material.Ti₃C₂X₂ and TMDs/Ti₃C₂X₂ are isotropic materials at small strains.Larger strains lead to severe divergence of stress-strain curves for Ti₃C₂X₂ and TMDs/Ti₃C₂X₂ zigzag（x-axis）and armchair（y-axis）,and the ideal strength on the x-axis of the heterogeneous junction is greater than the y-axis,and the critical strain on the x-axis is less than the y-axis.We analyze the variation pattern of the mechanical parameters of heterostructures and find that the mechanical failure of heterostructures is mainly related to the internal atomic arrangement and the difference of their bonding energy due to the capping of functional groups.The results of the study showed that TMDs/Ti₃C₂ have stable structures and rich electronic properties that are easily regulated by external fields.Functional groups have a significant impact on the mechanical and electrical properties of TMDs/Ti₃C₂.The mechanical properties of the TMDs/Ti₃C₂ have been discussed detailly and the micro-mechanism of its mechanical failure is discovered.Our results provide valuable insight into the combined effects of external field and novel functional groups on the related properties of TMDs/Ti₃C₂X₂.