Theoretical Study On The Geometric Structure And Electromagnetic Properties Of Ag_nM~? (n=1-16, M=Cr, Mn, ?=0, ±1) Clusters

As a kind of metal nanomaterial with fluorescence and catalysis functions,silver clusters have a good prospect in the application of chemistry and chemical engineering,material applications,biomedical applications and so on.In recent years,in order to explore more potential applications of silver clusters,the doping silver clusters have been studied and attracted much attention.However,there are few theoretical and experimental studies on the transition metal Cr and Mn doped silver clusters.Therefore,the geometric structure,spectral and electromagnetic characteristics of Ag_nM^?(n=1-16,M=Cr?Mn,?=0?±1)clusters are studied systematically and comprehensively in this paper.Firstly,geometric structure of Ag_nM^?(n=1-16,M=Cr?Mn,?=0?±1)clusters were optimized based on density functional theory and CALYPSO structure search method.The results show that in the Ag_nM^?ground state clusters,M atom is in a high coordination position.With the increase of the number of cluster atoms,M atom is gradually surrounded by Ag atom.When n=12,the icosahedral structure with M atom as the center is formed.When the number of atoms is more than 13,the ground state structure is basically based on the icosahedron,and the Ag atom grows on the surface of the icosahedron in the way of"triangular dense accumulation".The ultraviolet absorption spectra,infrared spectra and Raman spectra of Ag_nM^?clusters were obtained by calculation.The characteristic peaks of the infrared spectra correspond to the stretching vibration of Cr and Mn atoms.Secondly,the vertical ionization energy(VIP),electron affinity energy(EA),disintegration energy(DE),mean binding energy(E_b),HOMO-LUMO energy gap(E_g),photoelectron energy spectrum(PES)of Ag_nM^?(n=1-16,M=Cr?Mn,?=0?±1)clusters were studied by using the obtained ground state structure.In general,the vertical ionization energy of Ag_nM(M=Cr,Mn)and Ag_nMn^-decrease,the vertical ionization energy of Ag_nCr^-shows some odd-even oscillation,and the electron affinity energy of Ag_nM^0/-both increase.For the energy gap,the energy gaps of the ground state clusters of Ag_nCr(n=1-13)and Ag_nCr⁺(n=1-11,13-15)exhibit odd-even oscillation.Regarding the average binding energy,the E_b of Ag_nM^?ground state clusters increase gradually with the increase of the number of atoms,which indicate that the stability of Ag_nM^?ground state clusters increase gradually with the increase of cluster size.According to the photoelectron spectroscopy,the first strong absorption band of Ag_nM is located between 8-12 e V,while the first strong absorption band of Ag_nM^-is located between 4-8 e V.Finally,the total magnetic moment of the ground state Ag_nM^?clusters and the local magnetic moment of M atom,as well as the orbital charge and the orbital magnetic moment of M atom were also discussed.The magnetic moment of Ag_nCr(n=6-12)ground state clusters decrease gradually with the increase of the number of cluster atoms,until the magnetic moment is completely quenched;from the Ag₁₃Cr cluster,the magnetic moment increases gradually.The magnetic moment of Ag_nMn oscillate down between n=3 and 12 and increase gradually from n=13.The total magnetic moment of the ground state Ag_nM^?clusters mainly come from the M atom.The change of magnetic moment of M atom in Ag_nM cluster is mainly caused by charge transfer,which mainly comes from the charge transfer on the 3d orbital.