Theoretical Studies On The Structures,Electronic And Magnetic Properties Of Rh₇m（M=3d,4d） And Ni_mRh_n（m+n≤8） Clusters

In the field of material science,nano-clusters has always been a hot issue.The special microstructure and superior chemical and physics properties open a new world to the fundamental researches（that is,clarify the transition from micro atomic to macroscopic material）and the potential technological applications.It is widely used in chemical catalysis,biotechnology,magnetic materials,and optoelectronics.The properties of the binary metal clusters are dependent not only on the size,but also on the compositions and the chemical order,which can be designed and tailored to a certain degree.In many cases,synergistic effect can be found in a bimetallic system.there is an enhancement in specific properties.Therefore,many researchers are committed to finding alloy clusters with new founctionalities.Based on density functional theory to first-principles,the structural evolution,stabilities,electronic structure and magnetic properties of transition metal doped rhodium clusters Rh₇M（M=3d,4d）and small bimetallic Ni_mRh_n（m+n≤8）clusters are systematically investigated.The main contents are as follows:（1）Structural,Electronic and Tunable magnetic properties of transition metal doped Rh8cluster from First principles calculationThe configurations,electronic and magnetic properties of transition metal doped rhodium clusters Rh₇M（M=3d,4d）are systematically investigated at the DFT-GGA level.The results show that the most stable structures of the Rh₇M（M=3d）clusters prefer to possess a same configuration bicapped octahedron except Rh₇ Cr,while the energetically favorable configurations of the Rh₇M（M=4d）clusters have different degree of geometry reconstruction.In most cases,the mixed clusters show relatively higher binding energy,indicating that the presence of the impurity atoms could stabilize the pure rhodium cluster.The Rh₇M（M=3d,4d）have smaller frontier orbital energy gaps in comparison to the host,which shows that they are more active as far as chemical reactivity.The magnetic moments of Rh₇M（M=3d,4d）range from 3μB to 13μB and the doping of a Fe atom enhances the magnetic moment of the mixed cluster most,revealing that their magnetic properties can be tuned by varying composition.This will make them have a better application in the spintronic and magnetic storage materials.（2）Structures,chemical order,electronic structure,magnetic properties of small binaryNi-Rh clusters :First-principles studyDensity functional theory（DFT）for generalized gradient approximation calculations have been applied to study the structural evolution,chemical order,electronic and magnetic properties of small bimetallic Ni_mRh_n（m+n≤8）clusters.The effect of size and composition on the characteristics including the bong length,average binding energies,second finite difference energies,mixing energies,HOMO-LUMO gaps,chemical short-range order parameter σ,and magnetic moment of the particles are discussed.Structural motifs noted that the Rh atom prefers to segregate to maximize the number of Ni-Ni and Ni-Rh bonds.The stabilities of the mixed clusters is associated with the type and the number of bonds.The average binding energies increases monotonously with the increase of size and the number of Ni atoms.The calculations of mixing energies and σ noticed that the mixing is favorable for the considered clusters.The mixed cluster contains more Rh have smaller frontier orbital energy gaps,indicating the high reactivity.The doping of Rh into Ni clusters increase the d electron energy level.Alloy clusters with different chemical activity can be obtained by changing the constituent element proportion.All the optimized lowest energy structures show ferromagnetic–like order.A synergistic magnetic effects between the constituent elements was found in the bimetallic system.Not only the local Rh magnetic moment is increased,but also the Ni moments gets slightly enhanced.which is a consequence of both geometrical effects and hybridization originated from Ni-Rh.