A Theoretical Study On The Structure And Magnetic Properties Of Mn-TM (Transition Metal) Alloy Clusters

The study of bimetallic transition metal (TM) alloy clusters hasbeen active in the past few decades owing to their potentialapplications in catalysis, magnetic storage, optical and medical fields.At the nanoscale, bimetallic TM alloy clusters exhibit unusualelectronic, magnetic and catalytic properties due to their particularchemical and physical properties, which can be controlled bychanging the chemical composition and size. Therefore, theelectronic structure and magnetism of bimetallic TM alloy clustershas become one of the most active research subjects in the field ofcluster physics. In recent years, more and more theoretical andexperimental researches systematically and deeply invesitgate onthe bimetallic TM alloy clusters, but how to choose the dopingelements, composition, atomic arrangement and size to obtain thenew electromagnetic properties is still a key problem in clusterapplication research.In order to further understand the properties of bimetallic TM alloy clusters and better improve the fictionalization design of newnanomaterials, in this paper, we chose the Mn5cluster and Rhnclusteras the host cluster, and investigate the geometries; electronic andmagnetic properties of other TM and Mn atom doped the host cluster.The structures, electronic and magnetic properties of Mn4TM (TM=3d,4d) and RhnMn (n=1-12) clusters have been systematicallyinvestigated by using density functional theory. Our main objectivesof present work are to explore the influence of doping elements onthe structure and magnetic properties of pure clusters and theorigin of the magnetic behaviors. The main contents and results areas follows:1. Structural, electronic and magnetic properties of Mn4TM (TM=3d,4d) clustersThe geometries, stability, electronic and magnetic properties ofMn4TM (TM=3d,4d) clusters have been systematically studied byadopting the density functional theory with generalized gradientapproximation. Except Mn4Tc, the most stable structures for Mn4TMclusters are all the distorted triangular bi-pyramid structure with thetransition-metal atom at the vertex or at the middle plane. Thesystemic study in average binding energies and HOMO-LUMO energygap demonstrates that TM-doping could stabilize the host cluster. Forentire Mn4TM clusters, the total magnetic moments are increased in various degrees than that of pure Mn5cluster, except the Mn4Tc.Mn4Ni and Mn4Pd cluster possess a larger ferromagnetic alignmentmoment (20μB), which suggests their potential applications in newnano-materials as building blocks. The different doping atomsresulting in various magnetic properties are also elucidateddetailed in this paper.2. Structures, stability, electronic and magnetic properties of smallRhnMn (n=1–12) clustersThe structures, stabilities and magnetic properties of Rhn+1andRhnMn clusters (n=1-12) are investigated by using the densityfunctional theory. The overall structural evolutionary trend showsthat, except n=7,9and12, the Mn substitution doping almost does notbring much influence to the primary configurations, and the groundstate structure of RhnMn is still similar to that of the correspondingpure ones. Additionally, the Mn atom can be looked upon as asubstitutional impurity in the pure Rhn+1cluster. Meanwhile, the EbofRhnMn is decreases with the substitution of one Rh atom by one Mnatom, indicating the Mn-doping can weaken the energetic stability ofRh clusters. The stability analysis of entire RhnMn clusters indicatesthat the Rh3Mn, Rh5Mn, Rh8Mn and Rh11Mn clusters are more stablethan their neighbors. Moreover, the doping of Mn atoms causes theRhnMn clusters evident oscillation of magnetic behavior, and the origin of such a magnetic phenomenon is analyzed in detail.