Geometrical, electronic, and magnetic properties of small AunSc (n=1-8) clusters

Geometrical, electronic, and magnetic properties of the Sc-doped gold clusters, Au_nSc (n=1-8), have been studied using the density-functional theory within the generalized gradient approximation. An extensive structural search shows that the Sc atom in low-energy Au_nSc isomers tends to occupy the most highly coordinated position. The substitution of a Sc atom for an Au atom in the Au_n+1 cluster markedly changes the structure of the host cluster. Moreover, we confirm that the ground-state Au₆Sc cluster has a distortion to a lower D_2h symmetry. The relative stabilities and electronic properties of the lowest-energy Au_nSc clusters are analyzed based on the averaged binding energies, second-order energy differences, fragmentation energies, chemical hardnesses, and HOMO-LUMO gaps. It is found that the magic Au₃Sc cluster can be perceived as a superatom with high chemical stability and its HOMO-LUMO gap is larger than that of the closed-shell Zr@Au₁₄ cluster. The high symmetry and spin multiplicity of the Au₃Sc and Au₆Sc clusters are responsible for their large vertical ionization potential and electron affinity. The magnetism calculations indicate that the magnetic moment of the Sc atom in the ground-state Au_nSc (n=2-8) clusters gradually decreases for even n and is completely quenched for odd n.     

Structural,electronic and magnetic properties of Au<Subscript>n</Subscript>Pt (n = 1−12) clusters in comparison with corresponding pure Au<Subscript>n+1</Subscript> (n = 1−12) clusters

An all-electron scalar relativistic calculation on Au _n Pt (n = 1−12) clusters has been performed by using density functional theory with the generalized gradient approximation at PW91 level. Our results reveal that all the lowest energy geometries of Au _n Pt  (n = 1−12) clusters may be generated by substituting Pt atom for one gold atom of the Au _n+1 cluster at the highest coordinated site. Compared with corresponding pure Au _n+1 cluster, the lowest energy geometries of Au _n Pt clusters are distorted slightly and still keep the planar structures due to the strong scalar relativistic effect in small gold cluster. The Au-Pt bonds are stronger and most Au-Au bonds far from Pt atom are weaker than the corresponding Au-Au bonds in pure Au _n+1 cluster. By substituting Pt atom for one gold atom of Au _n+1 cluster at the highest coordinated site, the relatively stable and inactive odd-numbered Au _n+1 cluster becomes the relatively unstable and reactive odd-numbered Au _n Pt cluster, and the relatively unstable and reactive even-numbered Au _n+1 cluster becomes the relatively stable and inactive even-numbered Au _n Pt  cluster chemically and electronically. All the Au _n Pt clusters prefer low spin multiplicity. The even-numbered Au _n Pt clusters are found to exhibit zero magnetic moment and the odd-numbered Au _n Pt clusters are found to possess magnetic moment with the value of 1 μ _B. The odd-even alterations of magnetic moments and electronic configurations for Au _n Pt clusters are very obvious and may be simply understood in terms of the electron pairing effect.     

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.     

Geometrical,electronic, and magnetic properties of Au n V (n = 1–8) clusters: A density functional study

The geometrical, electronic, and magnetic properties of small Au _n V (n?=?1–8) clusters have been investigated using density functional theory at the PW91 level. An extensive structural search indicates that the V atom in low-energy Au _n V isomers tends to occupy the most highly coordinated position and the ground-state configuration of Au _n V clusters favors a planar structure. The substitution of a V atom for an Au atom in the Au _{n +1} cluster transforms the structure of the host cluster. Maximum peaks are observed for the ground-state Au _n V clusters at n?=?2 and 4 for the size dependence of the second-order energy differences, implying that the Au₂V and Au₄V clusters possess relatively higher stability. The energy gap of the Au₃V cluster is the largest of all the clusters. This may be ascribed to its highly symmetrical geometry and closed eight-electron shell. For ground-state clusters with the same spin multiplicity, as the clusters size increases, the vertical ionization potential decreases and the electron affinity increases. Magnetism calculations for the most stable Au _n V clusters demonstrate that the V atom enhances the magnetic moment of the host clusters and carries most of the total magnetic moment.     

Ab initio calculation of the geometric,electronic and magnetic properties of neutral and anionic Au n Pd (n = 1–9) clusters

The ab initio method based on density functional theory at the B3PW91 level has been applied to study the geometric, electronic, and magnetic properties of neutral and anionic Au _n Pd (n?=?1–9) clusters. The results show that the most stable geometric structures adopt a three-dimensional structure for neutral Au₇Pd and Au₈Pd clusters, but for anionic clusters, no three-dimensional lowest-energy structures were obtained. The relative stabilities of neutral and anionic Au _n Pd clusters were analysed by means of the dependent relationships between the binding energies per atom, the dissociation energies, the second-order difference of energies, the HOMO–LUMO energy gaps and the cluster size n, and a local odd–even alternation phenomenon was found. Natural population analysis indicates the sequential transfer from the Pd atom to the Au _n frame in Au_1,2,3,5Pd and Au_2,3Pd^? clusters, and from the Au _n frame to the Pd atom in other clusters. Much to our surprise, irrespective of whether it is the total magnetic moment or the local magnetic moment, the magnetic moment presents an odd–even alternation phenomenon as a function of the cluster size n. The magnetic effects are mainly localized on the various atoms (Au or Pd) for different cluster size n.     

Pt_nAl(n=1—8)小团簇的密度泛函理论研究

采用密度泛函理论方法,在BPW91/LANL2DZ水平下详细研究了Pt n Al(n=1—8)团簇的几何结构、稳定性和电子性质.同时,分析了团簇的结构演化规律、平均结合能、二阶能量差分、能隙、磁性、Mulliken电荷和电极化率.结果表明:除Pt2Al外,所有Pt n Al(n=1—8)团簇的基态几何结构都可以用Al原子替换Pt n+1基态构型中的Pt原子得到,且Al原子位于较高的配位点上.二阶能量差分、能隙的分析结果表明,PtAl和Pt4Al团簇相对其他团簇具有较高的稳定性.Mulliken电荷分析表明,Al原子所带的电荷转移到Pt原子上,Al原子是电荷的捐赠者.磁性的分析说明,单个Al原子的加入对Pt n团簇的平均每原子磁矩随尺寸的变化趋势没有影响,但总体上降低了Pt n团簇的平均磁矩.极化率的研究表明,富Pt团簇的非线形光学效应强,容易被外场极化.     

Structural, electronic and magnetic properties of Mn, Co, Ni in Gen for (n=1-13)

The structural, electronic and magnetic properties of TMGe_n (TM=Mn, Co, Ni; n=1-13) have been investigated using spin polarized density functional theory. The transition metal (TM) atom prefers to occupy surface positions for n<9 and endohedral positions for n≥9. The critical size of the cluster to form endohedral complexes is at n=9, 10 and 11 for Mn, Co and Ni respectively. The binding energy of TMGe_n clusters increases with increase in cluster size. The Ni doped Ge_n clusters have shown higher stability as compared to Mn and Co doped Ge_n clusters. The HOMO-LUMO gap for spin up and down electronic states of Ge_n clusters is found to change significantly on TM doping. The magnetic moment in TMGe_n is introduced due to the presence of TM. The magnetic moment is mainly localized at the TM site and neighbouring Ge atoms. The magnetic moment is quenched in NiGe_n clusters for all n except for n=2, 4 and 8.     

Electronic structure and magnetism in (CoPt)n(n⩽5) clusters

The geometrical and magnetic properties of bimetallic clusters (CoPt)_n(1?n?5) have been studied by using the generalized gradient correction spin density formalisms. In general, the ground state structures of (CoPt)_n clusters are the three-dimension structures. We found that both the binding energy and magnetism per (CoPt) unit are increasing consistently with the size of the Co–Pt cluster (n). However, as the n increases, the magnetism shows a trace of convergence while the binding energy shows a linearly increasing pattern. Generally, Co average magnetic moment is enhanced when alloyed with Pt atoms than that in pure Co clusters.     

A density functional theory study of small bimetallic PdnAl (n=1–8) clusters

The geometries, stabilities, and magnetic properties of Pd_nAl (n=1–8) neutral clusters are studied using density functional theory with generalized gradient approximation. The growth pattern for different sized Pd_nAl (n=1–8) clusters is Al-substituted Pd_n+1 clusters and it keeps the similar framework of the most stable Pd_n+1 clusters except n=6 and 8. Al atoms in the ground state Pd_nAl isomers tend to occupy the most highly coordinated position. The analysis of stabilities shows that doping an Al atom can enhance the stabilities of the host Pd clusters and the magic number characteristic of Pd₄ cluster cannot be changed, the Pd₃Al cluster has a higher stability. Charges are transferred from Al atom to Pd atoms in all Pd_nAl clusters, so the Al atom is the electron donor, and Pd atoms are the electron accepters. Doping an Al atom decreases the average atomic magnetic moments of the host Pd clusters.     

Effect of alloying on the stabilities and catalytic properties of Pt–Au bimetallic subnanoclusters: a theoretical investigation

Density functional theory (DFT) has been applied to study the geometrical and electronic structures and the catalytic properties for NO oxidation of pure Pt and PtAu clusters. The calculated results suggest that Pt₁₀ clusters shows the most stable structure among the pure Pt _n (n = 2–13) clusters with the local maximum Δ₂ E value. The doping of Au atoms reduces the stability of the clusters, and Pt₆Au₄ cluster has the most stable structure among Pt_10?n Au _n (n = 1–7) clusters, due to the closest band centers between Pt and Au atoms (0.83 eV) and the obvious s–p resonance peaks near the Fermi level. Pt₆Au₄ cluster displays the strongest activation of O₂ molecules among Pt_10?n Au _n (n = 0–7) clusters, owing to the clear overlap between O 2p and Pt 6 s and Au 6 s near the Fermi level, and the more positive d band center than the others. The interaction between NO and metals changes slightly in NO/Pt_10-nAu_n (n = 2–7) systems, which is weaker than that in NO/Pt₉Au system, as a result of the decreasing resonance peaks of sp hybridization near the Fermi level. Compared to pure Pt₁₀ cluster, the lower energy barriers and larger reaction energies on Pt₆Au₄ cluster suggest a higher catalytic activity of PtAu cluster for the O₂ dissociation and NO oxidation reactions. Our study provides atomic-scale insights into the nature of the interfacial effect that determines NO oxidation on PtAu cluster catalysts.     

Structures and magnetic properties of AunTi2+ (n $\leqslant$ 7) clusters

Base on the density-functional theory, the structural and magnetic properties of Au_nTi₂ ⁺ ( ) clusters are investigated. The two titanium atoms form a dimer in the gold clusters. The second-order energy differences and HOMO-LUMO gap provide a clear explanation of the abundance peaks and odd-even staggering observed recently in photofragmentation experiments. The magnetism of Au_nTi₂ ⁺ cluster shows an odd-even effect when n increases from 1 to 4 and drops to zero at n=5 and 7. The local magnetic moment and charge partition of Ti 4s, 3d orbitals are discussed. The peculiar magnetic properties are related to the structures and the hybridization between the Au 5d, 6s states and Ti 3d, 4s states.     

The 13-atom encapsulated gold cage clusters

The structure and the magnetic moment of transition metal encapsulated in a Au 12 cage cluster have been studied by using the density functional theory.The results show that all of the transition metal atoms(TMA) can embed into the Au 12 cage and increase the stability of the clusters except Mn.Half of them have the I h or O h symmetry.The curves of binding energy have oscillation characteristics when the extra-nuclear electrons increase;the reason for this may be the interaction between parity changes of extra-nuclear electrons and Au atoms.The curves of highest occupied molecular orbital-lowest unoccupied molecular orbital(HOMO-LUMO) gap also have oscillation characteristics when the extra-nuclear electrons increase.The binding energies of many M@Au 12 clusters are much larger than that of the pure Au 13 cluster,while the gaps of some of them are less than that of Au 13,so maybe Cr@Au 12,Nb@Au 12,and W@Au 12 clusters are most stable in fact.For magnetic calculations,some clusters are quenched totally,but the Au 13 cluster has the largest magnetic moment of 5 μ B.When the number of extra-nuclear electrons of the encapsulated TMA is even,the magnetic moment of relevant M@Au 12 cluster is even,and so are the odd ones.     

Geometrical,electronic, and magnetic properties of CunFe (n=1–12) clusters: A density functional study

The geometrical, electronic, and magnetic properties of small Cu_nFe (n=1–12) clusters have been investigated by using density functional method B3LYP and LanL2DZ basis set. The structural search reveals that Fe atoms in low-energy Cu_nFe isomers tend to occupy the position with the maximum coordination number. The ground state Cu_nFe clusters possess planar structure for n=2–5 and three-dimensional (3D) structure for n=6–12. The electronic properties of Cu_nFe clusters are analyzed through the averaged binding energy, the second-order energy difference and HOMO–LUMO energy gap. It is found that the magic numbers of stability are 1, 3, 7 and 9 for the ground state Cu_nFe clusters. The energy gap of Fe-encapsulated cage clusters is smaller than that of other configurations. The Cu₅Fe and Cu₇Fe clusters have a very large energy gap (>2.4 eV). The vertical ionization potential (VIP), electron affinity (EA) and photoelectron spectra are also calculated and simulated theoretically for all the ground-state clusters. The magnetic moment analyses for the ground-state Cu_nFe clusters show that Fe atom can enhance the magnetic moment of the host cluster and carries most of the total magnetic moment.     

Structural, electronic and magnetic properties of ConRh (n=1-8) clusters from density functional calculations

The geometries, stabilities, electronic and magnetic properties of Co_nRh (n=1-8) clusters have been investigated systematically within the framework of the generalized gradient approximation density-functional theory. The results indicate that the most stable structures of Co_nRh (n=1-8) clusters are all similar to those of corresponding Co_n+1 clusters. Maximum peaks of second-order energy difference are found at n=2, 4 and 7, indicating that these clusters possess relatively higher stability than their respective neighbors. The magnetism of the ground state of alloy clusters all displays ferromagnetic coupling except for Co₃Rh. In addition, the doped Rh atom exhibits an important influence on the magnetism of alloy clusters, e.g., compared with corresponding pure Co_n clusters, the local moment of Co atom is noticeably enhanced in Co_nRh alloy clusters at n=1, 2, 5, 6, 7 and 8, while reduced at n=3 and 4. Further analysis based on the average bond length, the charge transfer and the spin polarization has been made to clarify the different magnetic responses to Rh doping.     

Structural stability and electronic properties of Au5Hn (n=1–10) clusters

A systematic study on the geometrical structures, electronic and magnetic properties of Au₅H _n (n=1–10) clusters has been performed by using the all-electron scalar relativistic density functional theory with generalized gradient approximation at the PW91 level. It is found that all Au₅H _n clusters prefer to keep the planar structures like pure Au₅ cluster, the Au₅ structures in Au₅H₄, Au₅H₅ and Au₅H₆ clusters are distorted obviously. The adsorption of a number of hydrogen atoms enhances the stability of Au₅ cluster and all Au₅H _n clusters are more stable than pure Au₅ cluster energetically. The odd-even alteration of magnetic moment is observed in Au₅H _n clusters and may be served as the material with tunable code capacity of “0” and “1” by adsorbing odd or even number of H atoms. It seems that the most favorable adsorption between Au₅ cluster and a number of hydrogen atoms takes place in the case that the odd number of hydrogen atoms is adsorbed onto Au₅ cluster and becomes Au₅H _n cluster with even number of valence electrons.     

Geometries, stabilities, and electronic properties of Be-doped gold clusters: a density functional theory study

We have systematically investigated the geometrical structures, relative stabilities and electronic properties of small bimetallic AunBe (n = 1, 2, . . . , 8) clusters using a density functional method at BP86 level. The optimized geometries reveal that the impurity beryllium atom dramatically affects the structures of the Aun clusters. The averaged binding energies, fragmentation energies, second-order difference of energies, the highest occupied-lowest unoccupied molecular orbital energy gaps and chemical hardness are investigated. All of them exhibit a pronounced odd-even alternation, manifesting that the clusters with even number of gold atoms possess relatively higher stabilities. Especially, the linear Au2Be cluster is magic cluster with the most stable chemical stability. According to the natural population analysis, it is found that charge-transferring direction between Au atom and Be atom changes at the size of n = 4.     

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.     

All-electron relativistic calculation on Au5X (X = Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu and Zn) clusters

All-electron scalar relativistic calculations on Au₅X (X = Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu and Zn) clusters have been performed by using density functional theory with the generalized gradient approximation. Our calculation results indicate that all the lowest energy geometries of Au₅X clusters have planar structures; the doped X atoms prefer to occupy the fourfold coordination site. Except Au₅Fe, Au₅Co and Au₅Zn, for other clusters including pure Au₆ cluster, the HOMO are delocalized obviously with a contribution from all atoms in the cluster. On the contrary, the electron localization in Au₅Zn is very strong resulting in the least stability of this cluster. Au₅Cu cluster with six delocalized electrons being defined as magic number for two-dimensional system has the largest VIP and deepest HOMO energy level. With the substitution Au for X atoms, the metallicity of all Au₅X clusters is reinforced.     

Experimental g factor of hydrogenlike silicon-28

Using the first principles calculations, the mixed Au _n Zn _m ⁺ (n + m ?? 6) cluster cations and their monocarbonyls Au _n Zn _m CO⁺ have been investigated at the PW91 level. For the small Au _n Zn _m ⁺ , most ground-state isomers are planar structures. A significant odd-even oscillation of the highest occupied-lowest unoccupied molecular orbital energy gaps with the number of Au atoms is observed. Upon CO adsorption, the top site and C head-on adsorptions are most favorable in energy. Moreover, the optimized geometries indicate that the CO molecule prefers binding to Au atom of the Au _n Zn _m ⁺ clusters, which can be understood by the frontier molecular orbital theory in detail. From the theoretical calculations, the CO charge population, CO binding energy (BE) and the Gibbs free-energy change ??G generally decrease with the increase of the Zn content. It is found that the BE is highly related to the electron transfer between CO and the cluster cations. Furthermore, a linear correlation between ??G and the CO BE is found. The red shift in the CO stretching frequency is sensitive to the cluster size and composition. Our calculation suggests that CO reactive collision on Au₃Zn⁺ and Au₂Zn ₂ ⁺ may lead to the dissociation of the clusters with a Zn atom loss.     

密度泛函理论研究Run和RunAu(n=1-12)团簇的结构和电子性质

采用密度泛函理论中的广义梯度近似(GGA) 对 Ru_n Au和Ru_n 团簇的几何构型进行优化,并对能量、频率、电子性质和磁性质进行了计算. 结果表明,Ru_n Au团簇的最低能量结构可以通过Au原子代替Ru_n+1团簇中的Ru原子生长而成.除了局域的结构畸变,Ru_n Au和Ru_n+1团簇具有相似的几何结构.二阶能量差分、电离势、亲和势和分裂能表明Ru₅, Ru₈, Ru₅Au, Ru₈Au 是稳定的团簇,Au的掺杂没有改变Ru_n 的相对稳定性.通过电子性质的分析发现,当Au原子掺杂在Ru_n 中,团簇的化学活性增加,且团簇的能隙主要由电子的配对效应决定;对于大多数团簇来说,Au原子掺杂提高了Ru_n Au的磁矩. 关键词： n Au和Ru_n 团簇')" href="#">Ru_n Au和Ru_n 团簇 几何结构 电子性质