Theoretical Prediction Of Rhodium Phosphide Structures And Study On Electronic Structure Of Vertical Heterojunction Of Vanadium Disulfide

This paper includes two parts:one is the theoretical prediction of RhP structures,and the other is the study on the electronic structure of tVS₂/hVS₂ vertical heterostructure.RhP with an m:n ratio of 1 has been reported to be a novel cocatalyst for the photocatalyst CdS,which can improve the performance,reusability and lifetime of the CdS photocatalyst.However,the morphology,crystal geometry,and other intrinsic properties of RhP are still unknown.Thus,we used the CALYPSO code with the particle swarm optimization?PSO?algorithm to search for the stable RhP crystals,and used the first-principles calculation method based on density functional theory?DFT?to calculate the electronic properties,hydrogen storage and other properties of the stable RhP structures.The results are as follows:?1?We have predicted three stable three-dimensional?3D?metallic RhP structures,using the first-principles method combined with particle swarm optimization,named RhP-I,RhP-II,and RhP-III.All these structures are nonmagnetic.Using vibrational normal mode calculations,all these structures are predicted to be dynamically stable.Through molecular dynamics simulations,the RhP-I phase can survive at 1500 K,the RhP-II structure is predicted to be stable at 500 K,while the RhP-III structure is stable only in its ground state.The RhP-II and RhP-III phases also have porous structures which could accommodate small atoms or molecules.?2?We explore the potential of the three RhP systems for trapping lithium,hydrogen,oxygen,boron,nitrogen and carbon single atoms.By calculating the formation energy of the single atom in RhP structures,we found that the RhP-I structure does not attract the additional atoms;while the RhP-II and RhP-III structures possess an excellent ability to trap lithium,hydrogen,oxygen,and boron atoms.The energy barrier for Li diffusion inside the RhP-II structure is calculated based on the NEB?nudged elastic band?method,the diffusion barrier is about 0.42eV.The vanadium disulfide monolayer has been considered to be one of the most important members in the two-dimensional transition metal dichalcogenides?TMDs?family.The bulk and two-dimensional structures of VS₂ have intrinsic magnetism,it has potential applications in spintronic devices.The VS₂ monolayer includes two polymorphs:trigonal prismatic?hVS₂?and octahedral coordinated?tVS₂?.The two phases of the VS₂ monolayer are all ferromagnetic?FM?semiconductors.In this work,we calculated the band structures of VS₂monolayers by using three different methods;studied the structure stability,magnetism,and electronic properties of t VS₂/hVS₂ heterostructure.The results are as follows:?1?The electronic structures of tVS₂ and hVS₂ monolayers are calculated,we found that tVS₂ and hVS₂ monolayers are all FM semiconductors.The tVS₂ and hVS₂ phases are n-type and p-type semiconductors,respectively.The lattice and energy levels between t VS₂ and hVS₂match well with each other to be capable of forming an efficient p-n heterostructure.?2?We obtained the stable structure of tVS₂/hVS₂ heterostructure and its interface formation energy.Moreover,we calculated the total energies of tVS₂,hVS₂ and tVS₂/hVS₂heterostructure under the biaxial strain from-10%to 10%,and found that the energies of tVS₂/hVS₂ are lying between tVS₂ and hVS₂.Thus,the heterostructure is considered to be an intermediate state of the VS₂ monolayer.We also calculated the total energy of the tVS₂/hVS₂heterostructure with three magnetic structures,such as non-magnetic?NM?,ferromagnetic?FM?,and antiferromagnetic?AFM?state.The FM is the ground state for the t VS₂/hVS₂heterostructure.?3?We not only studied the electronic structure of the heterostructure,but also the influences induced by strains,defects,and rotated angles on its properties.The FM heterostructure is found to be a half-metal,with a type-I heterostructure in its spin-up channel,and the metallic property in the spin-down channel.The tVS₂/hVS₂ heterostructure presents a transition from half-metal to metal under the compressive strain,and a transition from half metal to metal and then to half-metal under the tensile strain,but the electronic transport occurs in the spin-up channel.The V vacancy can induce metallic properties of the heterostructure,and the S vacancy provides the tVS₂/hVS₂ heterostructure more peculiar electronic properties.The heterostructure with the interlayer rotation angle of 38.20°,27.80°,46.83°are half-metal,thus,the interlayer rotation angle have no significant effect on the electronic properties of the heterostructure.We predicted three RhP structures and studied their physical properties,using the first-principles method combined with particle swarm optimization.The RhP-I has thermodynamic and dynamically stability.The RhP-II and RhP-III phases also have porous structures which could accommodate H,Li,O,B small atoms or molecules.These properties provide the theoretical possibilities for potential applications of RhP crystals.Using the first-principles calculation based on the density functional theory,we investigated the electroninc structures of the tVS₂/hVS₂ heterostructure,as well as the effect of strain,vacancy,and interlayer rotation angle on its electronic properties.The results are significant for designing new p-n contacts and also for further exploration of spin transport.