Structures and electronic properties of AUn-1Cu and AUn （n ≤ 9） clusters

A systematic study on the structure and electronic properties of gold clusters doped each with one copper atom has been performed using the density functional theory. The average bond lengths in the Aun-1Cu （n ≤ 9） bimetallic clusters are shorter than those in the corresponding pure gold clusters. The ionization potentials of the bimetallic clusters Aun-1Cu （n 〈 9） are larger than those of the corresponding homoatomic gold clusters except for Aus. The energy gaps of the Au-Cu binary clusters are narrower than those of the Aun clusters except AuCu and Au3Cu. No obvious even-odd effect exists in the variations of the electron affinities and ionization potentials for the Aun-1Cu （n ≤ 9） clusters, which is in contrast to the case of gold clusters Aun.     

Structural,electronic,and magnetic properties in FeAlAu_n(n=1–6)clusters:A first-principles study

The geometries,electronic and magnetic properties of the trimetallic clusters Fe Al Aun(n = 1–6) are systematically investigated using density functional theory(DFT).A number of new isomers are obtained to probe the structural evolutions.All doped clusters show larger relative binding energies than pure Aun+2partners,indicating that doping with Fe and Al atoms can stabilize the Aun clusters.The highest occupied molecular orbital–lowest unoccupied molecular orbital(HOMO–LUMO) gaps,vertical ionization potentials and vertical electron affinities are also studied and compared with those of pure gold clusters.Magnetism calculations demonstrate that the magnetic moments of Fe Al Aun clusters each show a pronounced odd–even oscillation with the number of Au atoms.     

Chiral structures and tunable magnetic moments in 3d transition metal doped Pt₆ clusters

The structural, electronic, and magnetic properties of transition metal doped platinum clusters MPt 6 (M=Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, and Zn) are systematically studied by using the relativistic all-electron density functional theory with the generalized gradient approximation. Most of the doped clusters show larger binding energies than the pure Pt 7 cluster, which indicates that the doping of the transition metal atom can stabilize the pure platinum cluster. The results of the highest occupied molecular orbital (HOMO)-lowest unoccupied molecular orbital (LUMO) gaps suggest that the doped clusters can have higher chemical activities than the pure Pt 7 cluster. The magnetism calculations demonstrate that the variation range of the magnetic moments of the MPt 6 clusters is from 0 μ B to 7 μ B , revealing that the MPt 6 clusters have potential utility in designing new spintronic nanomaterials with tunable magnetic properties.     

First Principle Calculation on Aun Ag2 (n = 1 ～ 4) Clusters

The first-principles method based on density-functional theory is used to investigate the geometries of the lowest-lying isomers of Aun Ag2 (n = 1 ～ 4) clusters. Several low-lying isomers are determined, and many of them in electronic configurations with a high spin multiplicity. The stability trend of Ag-doped Aun clusters is compared to that of pure Aun clusters. Our results indicate that the inclusion of two Ag atoms in the clusters lowers the cluster stability, indicating higher stability as the structures grow in size. The bigger energy difference between the Aun and Aun Ag2 curves as the structures grows in size. This information will be useful to understanding the enhanced catalytic activity and selectivity gained by using silver-doped gold catalyst.     

Density-functional investigation of 3d,4d,5d impurity doped Au6 clusters

The general features of the geometries and electronic properties for 3d,4d,and 5d transition-metal atom doped Au 6 clusters are systematically investigated by using relativistic all-electron density functional theory in the generalized gradient approximation(GGA).A number of structural isomers are considered to search the lowest-energy structures of M@Au 6 clusters(M=3d,4d and 5d transition-metal atoms),and the transition metal atom locating in the centre of an Au 6 ring is found to be in the ground state for all the M@Au 6 clusters.All doped clusters,expect for Pd@Au 6,show large relative binding energies compared with a pure Au 7 cluster,indicating that doping by 3d,4d,5d transition-metal atoms could stabilize the Au 6 ring and promote the formation of a new binary alloy cluster.     

First Principle Calculation on AunAg2 （n = 1 - 4） Clusters

The first-principles method based on density-functional theory is used to investigate the geometries of the lowest-lying isomers of AunAg2 （n = 1 - 4） clusters. Several low-lying isomers are determined, and many of them in electronic configurations with a high spin multiplicity. The stability trend of Ag-doped Aun dusters is compared to that of pure Aun clusters. Our results indicate that the inclusion of two Ag atoms in the clusters lowers the cluster stability, indicating higher stability as the structures grow in size. The bigger energy difference between the Aun and AunAg2 curves as the structures grows in size. This information will be useful to understanding the enhanced catalytic activity and selectivity gained by using silver-doped gold catalyst.     

Density functional theory study of Mg2Nin （n = 1-8） clustersDensity functional theory study of Mg2Nin （n = 1-8） clustersDensity functional theory study of Mg2Nin （n = 1-8） clustersDensity functional theory study of Mg2Nin （n = 1-8） clustersDensity functional theory study of Mg2Nin （n = 1-8） clusters

The density functional theory B3PW91 with LANL2DZ basis sets has been used to study the possible geometries of Mg2Nin （n - 1-8） clusters. For the lowest energy structures of the clusters, stabilities, electronic properties, and natural bond orbital （NBO） are calculated and discussed. The results show that the doped Mg atoms reduce the stabilities of pure Ni clusters. The Mg2Ni2, Mg2Ni4, and Mg2Ni6 clusters are more stable than neighboring clusters. The system appears magic number characteristics. In addition, the hybridization phenomenon occurs, owing to the interaction of Mg and Ni. The result of charge transfer is that Ni atom is negative and the Mg atom is positive. We also conclude that the 3p and 4d orbitals of the Ni atom have an effect on the stabilities of the clusters.     

Density functional theory study of Mg_2Ni_n(n= 1–8) clusters

The density functional theory B3PW91 with LANL2DZ basis sets has been used to study the possible geometries of Mg2Nin(n = 1–8) clusters. For the lowest energy structures of the clusters, stabilities, electronic properties, and natural bond orbital(NBO) are calculated and discussed. The results show that the doped Mg atoms reduce the stabilities of pure Ni clusters. The Mg2Ni2, Mg2Ni4, and Mg2Ni6clusters are more stable than neighboring clusters. The system appears magic number characteristics. In addition, the hybridization phenomenon occurs, owing to the interaction of Mg and Ni. The result of charge transfer is that Ni atom is negative and the Mg atom is positive. We also conclude that the 3p and 4d orbitals of the Ni atom have an effect on the stabilities of the clusters.     

Chiral structures and tunable magnetic moments in 3d transition metal doped Pt6 clusters

The structural, electronic, and magnetic properties of transition metal doped platinum clusters MPt6 （M=Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, and Zn） are systematically studied by using the relativistic all-electron density functional theory with the generalized gradient approximation. Most of the doped clusters show larger binding energies than the pure Pt7 cluster, which indicates that the doping of the transition metal atom can stabilize the pure platinum cluster. The results of the highest occupied molecular orbital （HOMO） lowest unoccupied molecular orbital （LUMO） gaps suggest that the doped clusters can have higher chemical activities than the pure Pt7 cluster. The magnetism calculations demonstrate that the variation range of the magnetic moments of the MPt6 clusters is from 0 μB to 7 μB, revealing that the MPt6 clusters have potential utility in designing new spintronic nanomaterials with tunable magnetic properties.     

Structures, stabilities and magnetic moment of small copper-nickel clusters

This paper obtains the lowest-energy geometric structures and the electronic and magnetic properties of small CuNi_N clusters by using all-electron density functional theory. The calculated results reveal that the Cu atom prefers to occupy the apical site when N ≤ 9 and for the clusters with N=10, the Cu atom starts to encapsulate in the cage. The CuNi₇} and CuNi₉ are magic clusters. The magnetism correlates closely with the symmetry of the clusters. For these clusters, the charge tends to transfer from the nickel atoms to the copper atoms. It finds that the doping of Cu atom decreases the stability of pure Ni_N clusters.     

Insights into the structures,stabilities, electronic and magnetic properties of X2Aun (X = La,Y, and Sc; n = 1–9) clusters: comparison with pure gold clusters

A systematic study of the X₂Au_n (X = La, Y, Sc; n = 1–9) clusters are performed by using the density functional theory at TPSS level. The structures, stabilities, electronic, and magnetic properties are investigated in comparison with pure gold clusters. The results show that the transition points of the doped clusters from two-dimensional to three-dimensional structure are obviously earlier than gold clusters. The impurity X atoms tend to occupy the most highly coordinated position and form the largest probable number of bonds with gold atoms. In addition, the impurity atoms can strongly enhance the stabilities of gold clusters. It indicates that the impurity atoms dramatically affect the geometries and stabilities of the Au_n clusters. The highest occupied molecular orbital–lowest occupied molecular orbital gap, vertical ionisation potential, and chemical hardness show that the X₂Au₆ clusters have higher stabilities than the others. In La₂Au_1–9, Y₂Au_1–7, and Sc₂Au_1–4 clusters, the charges transfer from X atoms to the Au_n frames. The total magnetic moments of X₂Au_n clusters exist distinctly odd–even alternation behaviours except for La₂Au₄ and Sc₂Au₄ clusters.     

AunY(n＝1—9)掺杂团簇的结构和电子性质研究

采用相对论有效原子实势(RECP)近似和密度泛函(B3LYP)方法，选择LANL2DZ基组，优化得到了Au_nY(n＝1—9)二元掺杂团簇稳定的基态结构和电子性质.研究结果表明，掺杂Y原子的Au_nY(n＝1—9)团簇随n的变化，其电离势、电子亲合能和费米能级与Au_n(n＝2—9)一样具有“奇-偶”振荡效应；团簇离子的稳定性具有“幻数”现象，Au₂Y⁺和Au₆Y⁺比其他团簇离子更稳定，与质谱实验结果一致；同一团簇中，团簇最稳定的异构体(基态)是趋于Y原子有最大的邻近的Au原子数. 关键词： Au-Y团簇 密度泛函 平衡几何结构 电子性质     

激光吸收铒掺杂上转换材料的光谱特性实验分析

采用湿化学法制备了铒掺杂氧化钇上转换纳米粉体材料.研究了不同掺杂浓度、掺杂元素种类对材料显微结构、物相组成和光谱特性的影响.结果表明,通过控制掺杂元素的种类、掺杂浓度可以实现对光谱性能（包括光谱反射系数和上转换光谱）的调控.实验表明,该材料对106 μm激光具有较好的吸收性能. 关键词： 铒掺杂氧化钇纳米粉体 上转换材料 激光与红外复合隐身 光谱反射系数     

Size-selected Au clusters deposited on SiO2/Si: Stability of clusters under ambient pressure and elevated temperatures

This study examined the oxidation and reduction behavior of mass-selected Au clusters consisting of 2-13 atoms deposited on silica. An atomic oxygen environment was used for the oxidation of Au. X-ray photoelectron spectroscopy (XPS) was used to identify Au(III) and Au(O). Au₅, Au₇ and Au₁₃ clusters deposited on the as-prepared SiO₂/Si substrates were highly inert towards oxidation, whereas the other clusters could be oxidized, i.e. the chemical property drastically changed with the number of atoms in a cluster. The size-selectivity in chemical reactivity remained unchanged upon air-exposure. The chemical properties of the deposited Au clusters were unchanged after annealing at 250 °C. Annealing at higher temperatures caused structural changes to the surface, as determined by the oxidation behavior. XPS of the deposited Au clusters upon annealing indicated charge transfer from Au to silica.     

Density functional study of Agn-1Y (n=2-10) clusters

Employing the density functional theory, we investigate the lowest-energy geometric, the stable and the electronic properties of Ag_n-1Y (n=2-10) clusters in this paper. The structural optimization and the frequency analysis are performed at the B3LYP/LANL2DZ level. Meanwhile, the differences in geometry, stability and electronic properties between Ag_n and Ag_n-1Y (n=2-10) clusters are also studied. The results show that for the doping of the yttrium atoms, the structures and the average binding lengths of the Ag_n clusters are greatly changed. In addition, the thermodynamic stabilities of the Ag_n clusters are enhanced generally with the doping of the Y atoms. In addition, the chemical stabilities of the Ag_n-1Y clusters are still improved compared with that of the three-dimensional Ag_n clusters.     

Abnormally enhanced Eu emission in Y2O2SO4:Eu inherited from their precursory dodecylsulfate-templated concentric-layered nanostructure

A new nanostructure-mediated approach was demonstrated to synthesize Eu³⁺-doped yttrium oxysulfates Y₂O₂SO₄:Eu³⁺ giving rise to abnormally enhanced Eu³⁺ emission. Yttrium and europium salts, sodium dodecylsulfate (SDS), and urea at various Eu³⁺ concentrations were reacted in aqueous solution at 80, 85, and 87 °C to yield Eu³⁺-doped dodecylsulfate-templated yttrium oxide mesophases with straight-layered (S-type), concentric-layered (C-type) and layer-to-hexagonal transient-layered (T-type) structures, respectively. On calcination at 1000 °C, all of these mesophases were converted into Y₂O₂SO₄:Eu³⁺ to exhibit luminescence bands including the ⁵D₀-⁷F₂ transition with a tendency in intensity to saturate or reach a maximum at 10-12 mol% Eu doping. The Eu³⁺ emissions for Y₂O₂SO₄:Eu³⁺ mediated by the T- and C-type mesophases were enhanced in intensity by a factor of about two and three times, respectively, stronger than those for not only compositionally the same sulfate Y₂O₂SO₄:Eu³⁺ obtained from yttrium-based sulfates but also Y₂O₃:Eu³⁺ obtained in the SDS-free system. In contrast, the emission intensities for the S-type-mesophase-mediated Y₂O₂SO₄:Eu³⁺ were close to those for the latter sulfates. The abnormally enhanced emission is likely based on specific deformation of sulfate groups induced through the conversion of concentric dodecylsulfate-layers to straight sulfate-layers in the oxysulfate framework upon calcination.     

Theoretical analysis of structure, thermodynamic properties, and optical properties of Ge-doped amorphous SiO2

Different stable geometric configurations of Ge doped amorphous SiO₂ (a-SiO₂) system, originating from one, two, or three Si atoms in various places of the a-SiO₂ substituted by Ge atoms randomly have been investigated using interatomic potentials in this work. The most stable structures have been identified and corresponding evolutional rules obtained. The structural growth pattern for Ge-doped a-SiO₂ system is that Ge atoms tend to spread far away from each other and keep away from the center. Furthermore, the thermodynamic properties including speci?c heat, Debye temperature, vibrational entropy, and so on are calculated from the structure with 16 Si atoms of the constructed a-SiO₂ cell replaced by Ge atoms and with the biggest Ge-Ge distance. It can be seen that entropy of Ge doped system with larger specific heat is higher than that of the pure system with smaller specific heat. At last, optical properties including optical absorption spectrum and electron energy loss function of nGe-doped a-SiO₂ (n=0-3, 8) system is also obtained.     

Y2(Fe1-x-y,Coy,Crx)17化合 物的结构及居里温度

通过x射线衍射及磁测量手段研究了Y₂(Fe_1-y-x,Co_y,C r_x)₁₇化合物的结 构及居里温度.研究结果表明Y₂(Fe_1-y-x,Co_y,Crx)₁₇化合物具有六 角相的Th₂Ni₁₇型结构.随着x的增加，Y₂(Fe 关键词： 2(Fe_1-y-x')" href="#">Y₂(Fe_1-y-x y')" href="#">Co_y x)_{1 7}化合物')" href="#">Cr_x)_{1 7}化合物 x射线衍射 居里温度     

Probing the structural,electronic and magnetic properties of small Au4M (M = Sc–Zn) clusters

Density-functional method PW91 has been selected to investigate the structural, electronic and magnetic properties of Au₄M (M =Sc–Zn) clusters. Geometry optimisations show that the M atoms in the ground-state Au₄M clusters favour the most highly coordinated position. The ground-state Au₄M clusters possess a solid structure for M = Sc and Ti and a planar structure for M = V–Zn. The characteristic frequency of the doped clusters is much greater than that of pure gold cluster. The relative stability and chemical activity are analysed by means of the averaged binding energy and highest occupied molecular orbital and lowest unoccupied molecular orbital energy gap for the lowest energy Au₄M clusters. It is found that the dopant atoms can enhance the thermal stability of the host cluster except for Zn atom. The Au₄Ti, Au₄Mn and Au₄Zn clusters have relatively higher chemical stability. The vertical detachment energy, electron affinity and photoelectron spectrum are calculated and simulated theoretically for all the ground-state structures. The magnetism calculations reveal that the total magnetic moment of Au₄M cluster is mainly localised on the M atom and vary from 0 to 5 μ_B by substituting an Au atom in Au₅ cluster with different transition-metal atoms.     

Geometries, stabilities, and electronic properties of gold-magnesium (AunMg) bimetallic clusters

The geometrical structures, relative stabilities, and electronic properties of bimetallic Au_nMg (n=1-8) clusters have been systematically investigated by means of first-principle density functional theory. The results show that the ground-state isomers have planar structures for n=1-7. Here, the calculated fragmentation energies, the second-order difference of energies, the highest occupied-lowest unoccupied molecular orbital energy gaps, and the hardness exhibit a pronounced odd-even alternation, manifesting that the clusters, especially Au₂Mg, with even-number gold atoms have a higher relative stability. On the basis of natural population analysis, the charge transfer and magnetic moment are also discussed.