Theoretical Study On The Structural Evolution And Electromagnetic Properties Of Ag_n+1 And Ag_nM (n=1-16, M=Sc-V) Clusters

As a transition metal cluster,silver clusters are a pretty good catalyst in many important redox and polymerization reactions,and the special properties of Ag clusters have a wide application in physical,chemical and material fields.Recently,in order to obtain the desired structural,electronic,optical,magnetic,and catalytic properties of Ag clusters,transition-metal-doped silver clusters have been extensively studied both experimentally and theoretically.However,for the M-doped?M=Sc-V?Ag_n clusters,few previous studies have been made.Therefore,in this paper,the geometrical,electronic,and magnetic properties of Ag_n+1 and Ag_nM?n=1-16,M=Sc-V?clusters will be investigated by the density functional theory?DFT?.Firstly,the geometry optimizations of Ag_n+1 and Ag_nM?n=1-16,M=Sc-V?clusters were performed using density functional theory and CALYPSO structure prediction method,which have obtain a number of isomers.The results exhibits that all dopant of M atoms in the most stable Ag_nM isomers tend to occupy the most highly coordinated position.With regard to the three-dimensional structures,the ground state structures of Ag_nM(except for Ag₁₆V)clusters are entirely vary from that of corresponding Ag_n+1 clusters.In addition,the ground state structures of Ag_n+1 cluster are in accord with the result of earlier report.In the infrared and Raman spectra of Ag_n+1 and Ag_nM?n=1-16,M=Sc-V?clusters,The absorbed peaks of planar clusters are less than those of 3D configuration clusters,and the AgM dimer have the same infrared and Raman spectra.Meanwhile,all intense peaks of the doped Ag_nM clusters in infrared spectra correspond to the stretching and bending vibration of Ag-M bonds,respectively.Secondly,the relative stability,electronic properties and chemical activity of the ground states Ag_n+1 and Ag_nM?n=1-16,M=Sc-V?clusters are analyzed through the atomic averaged binding energy,dissociation energy and HOMO–LUMO energy gap.It is found from the atomic averaged binding energies that the stability of clusters increases gradually with increasing cluster size,and the dopant of M atom in Ag_n+1 clusters can enhance the stability of the host clusters,especially the Ag₁₅Sc,Ag₁₄Ti and Ag₁₂V clusters have relative higher stability.According to the calculation results of dissociation energy,the global maxima of the DE of the same kind of clusters are found in the Ag₁₅Sc,Ag₁₄Ti and Ag₁₂V clusters,indicating that they are more stable in all clusters,which is in accord with the analytical results based on the atomic averaged binding energy.With respect to vertical ionization potential?VIP?and electron affinity?EA?,the calculated values of silver clusters are in good agreement with experimental findings.Nevertheless,no experimental data are available for VIP and EA of Ag_nM clusters.The calculation results manifest that the VIP and EA of ground state Ag_n+1 clusters show an odd-even oscillation,while the doped Ag_nM clusters change this character.The EA of linear Ag_n M clusters is obviously smaller than that of planar and stereoscopic clusters,and the Ag₂clusters is higher in EA than that of AgM clusters with similar linear structure.In the case of the energy gap,it is found that the E_g of ground-state silver clusters and Ag_n Sc?n=2-16?clusters exhibit an odd-even oscillation.The doping of Ti atom increases the Eg of Ag_n clusters with odd n and reduces the E_g of Ag_n clusters with even n.The substitution of one V atom for an Ag atom in Ag_n clusters with even n decreases the E_g of the host cluster,but has little effect on the E_g of Ag_n clusters with odd n.Furthermore,Ag₁₅Sc and Ag₁₄Ti clusters have evidently large E_g,which can be perceived as superatom.Finally,the total magnetic moments of ground state clusters and the orbital charges and orbital magnetic moments of doped atoms are calculated and analyzed.Compared to the pure silver cluster,the Ag_n Sc cluster has the same magnetic moment except for n=1 and 7.The magnetic moments of AgnTi(except Ag₉Ti and Ag₁₂Ti)clusters show an odd-even oscillation which is opposite to that of Ag_n+1 clusters.The doping of V atom can raise the magnetism of small silver clusters,but has little impact on the magnetism of large silver clusters.Simultaneously,the dopant significantly alters the spin density of state?SDOS?,which has an intense band between-5 and-2 eV.The results of local magnetic moment analysis reveal that the local magnetic moment of the doped M atom is consistent with that of the ground state Ag_n M cluster,and the total magnetic moment of the doped cluster is chiefly derived from the 3d orbital of paramagnetic M atom.In addition,the charge transfer should be the main reasons for the magnetic moment alterations of the dopant atom.