第一性原理计算ZrnFe(n=2—13)团簇的基态结构及其磁性

从第一性原理出发，利用密度泛函理论中的广义梯度近似对Zr_nFe(n=2—13)团簇进行了结构优化、能量和频率计算.在充分考虑自旋多重度的前提下，对每一具体尺寸的团簇，得到了多个平衡构型，并根据能量高低确定了团簇的基态结构.综合团簇的结合能、二阶能量差分以及团簇的最高占据轨道和最低未占据轨道间的能隙可知Zr₅Fe，Zr₇Fe和Zr₁₂Fe团簇的稳定性相对较高，Zr₁₂Fe团簇的结构是具有I_h对称性的正二十面体，而且Zr₁₂Fe的稳定性在所有团簇中是最高的.另外，不仅Zr₅Fe，Zr₇Fe和Zr₁₂Fe团簇的稳定性相对较高，而且它们均为磁性团簇(而Zr_n团簇的磁矩在n≥5时已经发生了淬灭)，由此可知通过选择合适的掺杂元素可能得到高稳定的磁性团簇.从Mulliken布居分析结果可知，除了在Zr₁₂Fe团簇中Fe原子失去少量电荷外，其他团簇中Fe原子均从Zr原子那里得到了一定量电荷，即Fe原子在Zr_nFe(n=2—13，n≠12)团簇中是电子受体.     

密度泛函理论对ZrnPd团簇结构和性质的研究

用B3LYP/LANL2DZ方法对Zr_nPd(n =1—13)团簇的平衡几何结构、能量、频率、电子性质和磁性进行了计算.研究表明,Pd原子位于表面的异构体更为稳定,其中Zr₇Pd,Zr₁₂Pd团簇稳定性高,是幻数团簇,此外,相对于Zr_nCo与Zr_nFe团簇,Zr_nPd团簇参与化学反应的能力较弱,化学稳定性更     

Density Functional Theory Study on Electronic and Magnetic Properties of Mn-doped (MgO)n (n=2～10) Clusters

利用密度泛函理论方法优化了纯的和M_n原子掺杂的(MgO)_n (n=2～10)团簇的几何结构. 在Mn原子掺杂的氧化镁结构中, 获得了一系列的同分异构体和与之相对应的总能量.MnMg_n-1O_n(n=2～10)的几何构型显示Mn原子优先取代低配位的Mg原子. 结构稳定性分析表明,除了(MgO)₁₀团簇外,其它纯的和掺杂结构的平均结合能均随着团簇的增大而增强. MnMg_n-1O_n团簇的二阶能量差结果表明MnMg₅O₆和MnMg₈O₉比相邻的团簇表现出更高的相对稳定性. 除了MnMgO₂团簇的磁矩为3.00 μB外,其它掺杂结构的磁矩均为5 μB左右. 它们的磁性主要受电荷转移大小、原子在结构中的位置以及结构尺寸所影响.     

AunSc (n=2～13)团簇的第一性原理研究

采用密度泛函理论中的广义梯度近似(GGA)对Au_nSc(n=2～13)的几何构型进行优化,并对能量和电子性质进行了计算．结果表明,当n≤11时,Au_nSc的低能量结构是平面结构,且掺杂的Sc原子没有扰乱Au_n的框架;当n≥12,Sc原子陷入了金团簇所形成的笼内．二阶能量差分、分裂能、电离势、亲和势和能隙表明Au₃Sc、Au₅Sc、Au₇Sc、Au₉Sc、Au₁₁Sc和Au₁₃Sc是较稳定的团簇;掺杂的Sc原子提高了纯金团簇的稳定性且改变了纯金团簇化学活性的;当n≤11时,Au_nSc的磁矩在0.000～1.000 μB振荡;对于n≥12,Au_nSc的磁矩出现了猝灭．     

NaBn(n=1—9)团簇的几何结构和电子性质

应用密度泛函理论(DFT)中B3LYP方法在6-311+G(d)水平上计算并分析了 NaB_n(n=1—9)团簇的几何结构及电子性质. 同时, 讨论了团簇的平均结合能、能级间隙、二阶能量差分和极化率.研究表明:NaB_n(n=1—9) 团簇基态绝大多数为平面构型. 能级间隙和二阶能量差分结果表明NaB₃与NaB₅是幻数团簇. 另外, 对平均线性极化率和极化率的各向异性不变量研究表明基态NaB_n团簇的电子结构随B原子的增加虽然趋于紧凑, 但尚未形成特定的堆积方式.     

内嵌金属富勒烯Tcn和Tcn@C70的理论研究

系统地研究了内嵌金属富勒烯Tc_n和Tc_n@C₇₀的平衡态结构、电子和磁性性质．研究表明C₇₀能够内嵌Tc_n团簇(n≤9)．除了Tc₂团簇,当n≤5时,形成内嵌金属富勒烯Tc_n@C₇₀是放热的过程,而当n>5时,这种过程是吸热的．在内嵌过程中,Tc_n团簇的构型和电子结构都发生了相当大的变化．与单独的Tc_n团簇相比,Tc_n@C₇₀的总磁矩明显地降低．对体系的轨道分布,Hirshfeld分布和态密度进行了分析发现,在内嵌金属富勒烯体系里,电子可以通过Tc-C的有效杂化从Tc_n团簇向碳笼转移,从而使得体系的整体磁性降低．     

TiGen-(n=7~12)团簇的光电子能谱及密度泛函理论研究

利用光电子能谱及密度泛函理论计算对TiGe_n^-(n=7~12)团簇的几何结构及电子特性等进行了系统研究. 对于TiGe_n^-负离子及中性TiGe_n,在n=8时出现了钛原子半内嵌的船型结构;在n=9~11时,新增的锗原子加盖到这种船型结构上,逐步形成钛原子完全内嵌的结构. TiGe₁₂^- 团簇具有一种钛原子内嵌的变形六棱柱结构. 自然布居分析结果显示,对于n=8~12的TiGe_n^-/0 团簇,随着内嵌结构的形成,有电子从锗原子转移到钛原子,说明其电荷转移方式与结构演变密切相关.     

AlnC4-/0(n=2∽4)团簇的结构和成键性质: 光电子能谱和理论计算

本文采用尺寸选择的负离子光电子能谱与高精度理论计算,对Al_nC₄^-/0(n=2∽4))团簇的结构和成键性质进行了研究. Al₂C₄^-团簇负离子的最稳定结构是一个C_2v对称的平面结构,其中两个C₂单元与两个铝原子分别相连. Al₂C₄^-团簇负离子的次稳定结构是一个线型结构,两个铝原子位于C₄线型结构两端,能量仅比最稳定结构高0.05 eV. 中性Al₂C₄团簇是一个线型结构. Al₃C₄^-团簇负离子是一个平面结构,其中三个铝原子分别与两个C₂单元相连. 而中性Al₃C₄团簇则是一个V字型结构. Al₄C₄^-团簇负离子和中性Al₄C₄团簇均为C_2h对称的平面结构,四个铝原子分别位于两个C₂单元的末端. Al_nC₄^-/0(n=2∽4))团簇负离子的自适应自然密度配分的分析结果表明这些团簇中铝原子与C₂单元之间的化学键具有σ和π键特征.     

AunCo (n=1～7)团簇的密度泛函理论研究.

用B3LYP/LanL2DZ方法,系统研究了钴掺杂金团簇Au_nCo (n=1～7)可能的稳定结构和最低能量异构体的相对稳定性．确定了系列低能量异构体,部分异构体的电子态具有较高的自旋多重性．计算结果表明,除n=7外Au_nCo (n=1～7)团簇的基态几何结构为平面结构,Au₂Co为幻数团簇、具有较高的稳定性.     

Au2Gen-/0 (n=1∽8)团簇结构演化和电子性质的光电子能谱和理论计算研究

本文利用尺寸选择的负离子光电子能谱和理论计算探索Au₂Ge_n^-/0 (n=1∽8)团簇的结构演化和电子性质. 通过比较理论模拟谱与实验谱,并使用CCSD(T)理论方法计算异构体的相对能量,从而确定金锗混合团簇的全局最小结构. 本文发现Au₂Ge_n^-/0 (n=1∽8)团簇的两个Au原子具有较高的配位数和较弱的亲金相互作用. 负离子团簇和中性团簇的最稳定结构分别处于自旋双重态和自旋单重态. 除了Au₂Ge₄^-/0和Au₂Ge₅^-/0,负离子团簇和中性团簇的全局最小结构具有相似的结构特点. Au₂Ge₁^-/0团簇是一个C_2v对称的V形结构,而Au₂Ge₂^-/0团簇是一个C_2v对称的双桥连结构. Au₂Ge₁^-负离子团簇是两个Au原子盖帽的Ge₄四面体结构,而Au₂Ge₄中性团簇是两个Au原子盖帽的Ge₄菱形结构. Au₂Ge_5∽8^-/0团簇主要采用三棱柱、四棱柱、及五棱柱结构. Au₂Ge₆是一个C_2v对称的四棱柱结构,并表现出σ和π双键性质.     

Geometries,stabilities, electronic and magnetic properties of small PdnIr (n = 1–8) clusters from first-principles calculations

The geometrical structures, relative stabilities, electronic and magnetic properties of small Pd_nIr (n = 1–8) clusters have been systematically investigated using density functional theory at the B3PW91 level. The optimised geometries show that the lowest-energy structures of Pd_nIr clusters prefer a three-dimensional configuration. The relative stability of these clusters was examined by analysis of the binding energies per atom, fragmentation energies, the second-order difference of energies and the HOMO–LUMO energy gaps as a function of cluster size. The obtained results exhibit that the Pd₂Ir, Pd₃Ir and Pd₅Ir clusters are more stable than their neighbouring clusters. The energy gap of the Pd₂Ir cluster is the largest of all the clusters (2.258 eV). In addition, the charge transfers, vertical ionisation potentials, vertical electron affinities and chemical hardness were calculated and discussed. The magnetism calculations indicate that the total magnetic moment of Pd_nIr clusters is mainly localised on the iridium atom for Pd_1–6Ir clusters. Meanwhile, the 5d orbital plays the key role in the magnetic moment of the iridium atom.     

密度泛函理论研究BnNi(n=6—12)团簇的结构和磁性

基于第一性原理,用密度泛函理论中的广义梯度近似(generalized gradient approximation,GGA)方法,在充分考虑自旋多重度的前提下,优化并得到了B_n(n=6—12)和B_nNi(n=6—12)团簇的平衡构型,按照能量最低原理确定其基态结构. B_n团簇的计算结果与已有的理论结果相一致. 当Ni原子掺杂在B_n团簇 关键词： nNi团簇')" href="#">B_nNi团簇 基态结构 磁性     

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.     

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.     

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

Equilibrium geometries, relative stabilities, and magnetic properties of small Au_nMn (n=1-8) clusters have been investigated using density functional theory at the PW91P86 level. It is found that Mn atoms in the ground state Au_nMn isomers tend to occupy the most highly coordinated position and the lowest energy structure of Au_nMn clusters with even n is similar to that of pure Au_n+1 clusters, except for n=2. The substitution of Au atom in Au_n+1 cluster by a Mn atom improves the stability of the host clusters. Maximum peaks are observed for Au_nMn clusters at n=2, 4 on the size dependence of second-order energy differences and fragmentation energies, implying that the two clusters possess relatively higher stability. The HOMO-LUMO energy gaps of the ground state Au_nMn clusters show a pronounced odd-even oscillation with the number of Au atoms, and the energy gap of Au₂Mn cluster is the biggest among all the clusters. The magnetism calculations indicate that the total magnetic moment of Au_nMn cluster, which has a very large magnetic moment in comparison to the pure Au_n+1 cluster, is mainly localized on Mn atom.     

Structural, electronic and magnetic properties of Fen@C60 and Fen@C80 (n=2-7) endohedral metallofullerene nano-cages: First principles study

We studied the structural, electronic and magnetic properties of small Fe_n clusters (n=2-7) endohedrally doped in icosahedral C₆₀ and C₈₀ fullerenes using first principles calculations based on the density functional theory. It is found that the encapsulated Fe_n clusters inside icosahedral C₈₀ are energetically favorable while Fe_n@C₆₀ metallofullerene nano-cages are not. The binding energies of the Fe_n encapsulated in C₆₀ are positive and increase with the number of iron atoms (n) while those of the Fe_n@C₈₀ are negative and their absolute values increase up to n=6. The encapsulation does not significantly change the enclosed cluster structure, but the total magnetic moment of the larger clusters reduces due to a stronger Fe-C hybridization.     

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.     

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.     

(OsnN)0,±(n=1-6)团簇电子结构与光谱性质的理论研究

采用密度泛函理论中的杂化密度泛函B3LYP方法在赝势基组LANL2DZ水平上对Os_nN^0,±(n=1-6)团簇的各种可能构型进行了几何结构优化,得出了它们的基态构型,并对基态结构的磁学性质、自然键轨道(NBO)、光谱和芳香性进行了理论研究. 研究结果表明:OsN^-和Os₅N^-团簇发生了"磁矩猝灭"的现象,在Os₂N和Os₄N< 关键词： nN^0,±(n=1-6)团簇')" href="#">Os_nN^0,±(n=1-6)团簇 电子结构 光谱性质 密度泛函理论     

Structures,energetics and magnetic properties of (NiSn)<Subscript><Emphasis Type="Italic">n</Emphasis></Subscript> clusters with <Emphasis Type="Italic">n</Emphasis> = 1–6

We report the results of calculations which were performed to investigate equilibrium structures, electronic and magnetic properties of stoichiometric (NiSn) _n clusters with n = 1–6 within the framework of density functional theory. The calculated results show that the structural arrangement of (NiSn) _n clusters is dominated by the Ni-Sn and Ni-Ni interactions. We find that these binary clusters show significant variation in the geometries as compared to that of the host nickel clusters. The preference for tetrahedron unit of Ni₃Sn is seen in the lowest-energy configuration of these clusters. The multi-centre bonding between Ni atoms play an important role in stabilizing the stoichiometric Ni-Sn clusters. Doping of Sn atoms enhances the binding energy and reduces the ionization potential of nickel clusters. These binary clusters prefer the lowest spin state. For (NiSn)₆ the magnetic moment is 0 μB. The complete quenching of the cluster magnetic moment appears to be due to the antiferromagnetic alignment of atomic spins as revealed by the spin density plots.