FeBN(N≤6)团簇的结构与磁性

利用密度泛函理论中的广义梯度近似(GGA)，在考虑自旋多重度后，预测了FeB_N(N≤6)团簇的基态结构.结果表明基态团簇的自旋多重度分别为4，3，2，1，2和1，其中FeB₄团簇比较稳定.同时对FeB_N(N≤6)基态团簇的磁性做了系统地研究，发现除了FeB₅团簇外，FeB_N(N≤6)团簇的总磁矩和Fe原子磁矩随团簇尺寸的增大而减小. 关键词： N团簇')" href="#">FeB_N团簇 自旋多重度 磁矩     

密度泛函理论计算GenFe(n=1—8)团簇的基态结构及其磁性

基于第一性原理，利用密度泛函理论中的广义梯度近似 (GGA)对Ge_nFe(n=1—8)团簇进行了结构优化、能量及频率的计算，得到了 Ge_nFe(n=1—8)团簇在不同自旋多重度下的平衡构型及其基态结构.结果表明：Ge_nFe混合团簇的平均结合能明显比相应纯锗团簇的平均结合能有所增大，即掺杂Fe原子可以提高锗团簇的稳定性；纯锗团簇的基态除了Ge₂为自旋三重态外其他均为单重态，而混合团簇Ge_nFe(n=1—8)的基态均为自旋三重态；对Ge_nFe(n=1—8)团簇的磁性做了较系统的研究，发现团簇总磁矩随团簇尺寸增大基本稳定在2μ_B (只有Ge₈Fe的总磁矩2.391μ_B较明显地偏离了2μ_B)，另外团簇中Fe原子的磁矩在2.5μ_B左右振荡. 关键词： nFe团簇')" href="#">Ge_nFe团簇 密度泛函理论(DFT) 自旋多重度 磁矩     

Mn(SiO2)3(M=Fe,Co,Ni;n=1-3)团簇的几何结构、光电性质及磁性

基于密度泛函理论中的广义梯度近似系统研究M_n(SiO₂)₃(M=Fe,Co,Ni;n=1-3)团簇的几何结构、光电性质和磁学性质.结果表明:Fe,Co原子相对于Ni原子更易于在(SiO₂)₃团簇上聚集;通过分析团簇的分裂途径及其产物,发现稳定性较好的氧化硅是一种很好的用于负载过渡金属"岛膜"的载体材料;M_n(SiO₂)₃团簇的能隙恰好位于近红外光谱范围内.通过磁性分析发现,该复合团簇的磁矩主要局域在过渡金属原子周围,而且,Fe₂(SiO₂)₃和Co₃(SiO₂)₃具有相对较大的磁矩,这主要源于过渡金属原子的d轨道间相互耦合.能隙和磁性两方面性质进一步肯定了二氧化硅磁性复合材料在医学界被用作光动力靶向治疗的可观前景.     

FeBN(N≤15)团簇结构、电子性质和磁性的密度泛函理论研究

采用密度泛函理论中的广义梯度近似(Generalized Gradient Approximation, GGA)方法, 对不同自旋多重度的FeBN(N≤15)团簇的平衡几何结构、电子性质和磁性进行了研究. 团簇基态结构的平均结合能、二阶能量差分和能隙均表明FeB8、FeB12和FeB14团簇较相邻团簇稳定. 团簇基态结构中Fe原子的d轨道和B原子的p轨道存在着明显的杂化. 团簇基态结构的总磁矩主要来自Fe原子3d轨道的贡献, 且总磁矩随团簇尺寸增大呈现奇偶振荡.     

FeBN (N≤3)团簇的结构与磁性

基于第一性原理,利用密度泛函理论中的广义梯度近似(GGA)对FeBN(N≤3)团簇进行了结构优化、能量和频率的计算,得到了FeBN(N≤3)团簇在不同自旋多重度下的平衡结构并确定了团簇的基态构型.结果表明,FeBN(N≤3)基态团簇的自旋多重度分别为4、3、2.我们对FeBN基态团簇的磁性做了系统的研究,得出了Fe原子磁矩和团簇总磁矩随团簇尺寸增大而减小的结论.     

密度泛函理论对CoBen(n=1—12)团簇结构和性质的研究

采用密度泛函理论中的广义梯度近似(GGA)对CoBe_n(n=1—12)团簇的几何构型进行优化，并对能量、频率和磁性进行了计算，同时考虑了电子的自旋多重度.得到了CoBe_n(n=1—12)团簇最低能量结构的自旋多重度是2和4.在CoBe_n(n=1—12)团簇中，Co原子的磁矩出现了奇偶振荡，当n=6时，Co原子的4s，3d和Be原子的2s，2p较强杂化、Co-Be键长的减小以及对称性的降低导致Co原子的磁矩最小.通过对CoBe_n(n=1—12)团簇电子性质的分析，得出了掺杂可以增强团簇稳定性和有利于增加合金化学活性的结论.n=5，10是团簇的幻数. 关键词： n团簇')" href="#">CoBe_n团簇 自旋多重度 磁矩 电子性质     

CoAlN(N=2-11)团簇基态结构的稳定性和磁性

采用密度泛函理论中的广义梯度近似(GGA),对CoAlN(N=2-11)团簇进行构型优化和磁性计算.在考虑自旋多重度的情况下得到了团簇的平衡构型及基态结构,并重点讨论了Co原子的sp-d杂化效应对体系稳定性和磁性的影响.结果表明:N为偶数时,团簇的基态为自旋双重态,Co原子磁矩随N增加整体上呈减小趋势;N为奇数时(除N=5为自旋三重态外),团簇的基态为自旋单重态,Co原子磁矩为零.N≥8时,Co原子陷入主团簇内部,体系的对称性降低,稳定性增强;轨道杂化增强了体系的稳定性,但减小了双重态和三重态体系中Co原子的磁矩;N=3,8,10是团簇CoAlN(N=2.11)的幻数.     

密度泛函理论研究Zrn(n=2—16)团簇的基态结构及其稳定性

从第一性原理出发，利用密度泛函理论中的广义梯度近似(GGA)对Zr_n(n=2—16)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、离解能、二阶能量差分以及团簇的最高占据轨道(HOMO)和最低未占据轨道(LUMO)间的能隙可知Zr₂，Zr₅，Zr₇，Zr₁₃ 关键词： n团簇')" href="#">Zr_n团簇 密度泛函理论(DFT) 基态结构 自旋多重度     

FeBN(N≤6)团簇的结构与磁性

利用密度泛函理论中的广义梯度近似(GGA),在考虑自旋多重度后,预测了FeBN(N≤6)团簇的基态结构.结果表明基态团簇的自旋多重度分另4为4,3,2,1,2和1,其中FeB4团簇比较稳定.同时对FeBN(N≤6)基态团簇的磁性做了系统地研究,发现除了FeB5团簇外,FeBN(N≤6)团簇的总磁矩和Fe原子磁矩随团簇尺寸的增大而减小.     

(OsH_2)_n(n=1~5)团簇结构稳定性与磁学性质的理论研究

采用密度泛函理论,在广义梯度近似(GGA)下对(Os H2)n(n=1~5)团簇的可能构型进行几何参数全优化,得到基态结构,并对基态结构的平均结合能(Eb)、能量二阶差分(Δ2E)、磁矩和态密度等进行计算.结果表明:(Os H2)n(n=1~5)团簇趋向于形成空间三维结构,Os与H之间有较强的相互作用,并且Os H2的基态结构可以看作是(Os H2)n(n=1~5)团簇结构的基本组成单元;(Os H2)4团簇稳定性较好,只有(Os H2)5基态结构呈反铁磁性耦合,团簇的磁矩主要来源于Os原子的d轨道.     

Density functional study of structural and electronic properties of Al<Subscript><Emphasis Type="Italic">n</Emphasis></Subscript>P (2 ≤ <Emphasis Type="Italic">n</Emphasis> ≤ 12) clusters

Low-lying equilibrium geometric structures of Phosphorus-doped aluminum cluster Al _n P (n = 2–12) clusters obtained by an all-electron linear combination of atomic orbital approach, within spin-polarized density functional theory, are reported. The binding energy, dissociation energy, and stability of these clusters are studied within the local spin density approximation (LSDA) and the three-parameter hybrid generalized gradient approximation (GGA) due to Becke-Lee-Yang-Parr (B3LYP). Ionization potentials, electron affinities, hardness, and static polarizabilities are calculated for the ground-state structures within the GGA. It is observed that symmetric structures with the P atom occupying a peripheral position are lowest-energy geometries of Al _n P (n = 2, 4–11), while the P impurities of Al₃P and Al₁₂P prefer to occupy internal sites in the aluminum clusters. Generalized gradient approximation extends bond lengths as compared to the LSDA lengths. The odd-even oscillations in the dissociation energy, the second differences in energy, the HOMO–LUMO gaps, the ionization potential, the electron affinity, and the hardness are more pronounced within both GGA and LSDA. The stability analysis based on the energies clearly shows the clusters with an even number of valence electrons are more stable than clusters with odd number of valence electrons.     

(CoMn)n(n=1~5)合金团簇的结构和磁性

采用密度泛函理论中的局域自旋密度近似和广义梯度近似对(CoMn)n(n=1～5)团簇的几何构型进行优化、能量、频率和磁性计算,确定了团簇的基态,对其基态的磁性和电子结构进行了系统研究,并与相对应的一元团簇进行了结构和磁性比较.研究表明,两种方法确定的基态构型基本一致,当n=1～4时,等比CoMn二元合金团簇的几何形状仍与一元团簇相同;(CoMn)3和(CoMn)4团簇出现了磁性双稳态,显示铁磁性和反铁磁性耦合;二元CoMn合金团簇中Co、Mn原子磁性仍能保持一元Co、Mn团簇基态的磁性.     

阻挫三角反铁磁YMnO3电子结构和磁性研究

基于广义梯度近似(GGA)的密度泛函理论,从非共轴的磁性结构出发,运用第一性计算得到了自旋阻挫反铁磁YMnO3的电子结构和磁性.考虑在位库仑势作用(U),研究了d电子关联作用对电子结构、能隙、和磁性的作用.计算得到,由于电子强关联和自旋阻挫的作用,Mn3d和O2p的电子态密度分布发生很大变化,费米面附近的基态能隙变大,Mn3d和O2p态电子杂化减弱,Mn离子的磁矩增加到3.92μB.我们的结果比局域化自旋密度近似LSDA计算结果更好地符合于实验测量值.     

V,Cr,Mn掺杂MoS2磁性的第一性原理研究

基于第一性原理的自旋极化密度泛函理论分别研究了过渡金属V, Cr, Mn掺杂单层MoS₂的电子结构、 磁性和稳定性. 结果表明: V和Mn单掺杂均能产生一定的磁矩, 而磁矩主要集中在掺杂的过渡金属原子上, Cr单掺杂时体系不显示磁性. 进一步讨论双原子掺杂MoS₂ 体系中掺杂原子之间的磁耦合作用发现, Mn掺杂的体系在室温下显示出稳定的铁磁性, 而V掺杂则表现出非自旋极化基态. 形成能的计算表明Mn掺杂的MoS₂体系相对V和Cr 掺杂结构更稳定. 由于Mn掺杂的MoS₂ 不仅在室温下可以获得比较好的铁磁性而且其稳定性很高, 有望在自旋电子器件方面发挥重要的作用. 关键词： 2')" href="#">单层MoS₂ 掺杂 铁磁态 第一性原理     

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.     

Ab initio study of neutral (TiO2)n clusters and their interactions with water and transition metal atoms

We have systematically investigated the growth behavior and stability of small stoichiometric (TiO(2))(n) (n = 1-10) clusters as well as their structural, electronic and magnetic properties by using the first-principles plane wave pseudopotential method within density functional theory. In order to find out the ground state geometries, a large number of initial cluster structures for each n has been searched via total energy calculations. Generally, the ground state structures for the case of n = 1-9 clusters have at least one monovalent O atom, which only binds to a single Ti atom. However, the most stable structure of the n = 10 cluster does not have any monovalent O atom. On the other hand, Ti atoms are at least fourfold coordinated for the ground state structures for n ≥ 4 clusters. Our calculations have revealed that clusters prefer to form three-dimensional structures. Furthermore, all these stoichiometric clusters have nonmagnetic ground state. The formation energy and the highest occupied molecular orbital (HOMO)-lowest unoccupied molecular orbital (LUMO) gap for the most stable structure of (TiO(2))(n) clusters for each n have also been calculated. The formation energy and hence the stability increases as the cluster size grows. In addition, the interactions between the ground state structure of the (TiO(2))(n) cluster and a single water molecule have been studied. The binding energy (E(b)) of the H(2)O molecule exhibits an oscillatory behavior with the size of the clusters. A single water molecule preferably binds to the cluster Ti atom through its oxygen atom, resulting an average binding energy of 1.1 eV. We have also reported the interaction of the selected clusters (n = 3, 4, 10) with multiple water molecules. We have found that additional water molecules lead to a decrease in the binding energy of these molecules to the (TiO(2))(n) clusters. Finally, the adsorption of transition metal (TM) atoms (V, Co and Pt) on the n = 10 cluster has been investigated for possible functionalization. All these elements interact strongly with this cluster, and a permanent magnetic moment is induced upon adsorption of Co and V atoms. We have observed gap localized TM states leading to significant HOMO-LUMO gap narrowing, which is essential to achieve visible light response for the efficient use of TiO(2) based materials. In this way, electronic and optical as well as magnetic properties of TiO(2) materials can be modulated by using the appropriate adsorbate atoms.     

Density functional study of the half-metallic ferromagnetism in Co-based Heusler alloys Co2MSn (M = Ti, Zr, Hf) using LSDA and GGA

The half-metallic state in the Heusler alloys Co₂MSn (M = Ti, Zr, Hf) was studied by means of first principles calculation, using both, the Local Spin Density Approximation (LSDA) and the Generalized Gradient Approximation (GGA) to the exchange-correlation energy. While the GGA calculation shows that the three alloys are half-metallic ferromagnets, the LSDA results show that they are ferromagnetic but not half-metallic systems. The difference between the exchange-correlation functionals is analyzed through the electronic structure of the alloys. The origin of the gap in the minority spin channel for GGA calculations is discussed.     

密度泛函理论的不同方法研究小钨团簇的结构与稳定性

分别利用密度泛函理论的LSDA方法和B3LYP 方法在有效核势基组(LanL2DZ)水平上系统地研究了Wn(n=2-14)团簇的结构和稳定性.Wn(n=2-14)团簇全局能量最小的最稳定结构被确定.结果表明:在所讨论的尺寸范围内,LSDA方法比B3LYP 方法得到的平均结合能与一阶能量差分高;大部分Wn(n=2-14) 团簇在两种方法计算下具有相同的几何结构.两种方法计算结果均表明:除了W3自旋多重度为3重态外,其余尺寸团簇的自旋多重度均为单重态;n=7的最低能量结构为双戴帽五边环,而非正十面体,n=8-10为笼型结构,n=11-14为扁长型结构.综合平均结合能、一阶能量差分和二阶能量差分,两种计算方法均表明Wn(n=2-14)团簇具有相同的幻数序列(2,6,9 和 13).     

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.