Evolution of geometrical structures,stabilities and electronic properties of neutral and anionic Li n Cu λ (n = 1–9, λ = 0, −1) clusters: compare with pure lithium clusters

The structural evolution, stabilities, and electronic properties of copper-doped lithium Li _n Cu^λ (n?=?1–9, λ?=?0, ?1) clusters have been systematically investigated using a density functional method at PW91PW91 level. Extensive searches for ground-state structures were carried out, and the results showed the copper tends to occupy the most highly coordinated position and form the largest probable number of bonds with lithium atoms. By calculating the binding energies per atom, fragmentation energies and the HOMO-LOMO gaps, we found LiCu, Li₇Cu, LiCu^?, Li₂Cu^? and Li₈Cu^? clusters have the stronger relative stability and enhanced chemical stability. The content and pattern of frontier MOs for the most stable doped isomers were analysed to investigate the bond nature of interaction among Li and Cu atoms. The results show some σ-type and π-type bonds are formed among them, and with small admixture of the Cu d characters. To achieve a deep insight into the electron localization and reliable electronic structure information, the natural population analysis and electron localization function were performed and discussed.     

Spin-polarised DFT study of cobalt-doped gallium clusters

The structural, electronic and magnetic properties of small gallium clusters doped with Cobalt have been studied using spin-polarised density functional theory. The binding energy per atom, second-order differences of total energies and fragmentation energies of equilibrium geometries of the host Ga_n+1 and doped Ga_nCo (n = 1–12) clusters are computed. Doped clusters are found to be more stable than pure Ga clusters; Ga₃Co, Ga₅Co and Ga₈Co clusters are exceptionally stable. Doping with Co changes the highest occupied molecular orbital-lowest unoccupied molecular orbital (HOMO–LUMO) gap, and also affects the magnetic moments of clusters.     

Evolution of structures,stabilities, and electronic properties of anionic [AunRb]− (n = 1–10) clusters: comparison with pure gold clusters

The geometric structures, stabilities, and electronic properties of small size anionic [Au_nRb]^? and Au_n+1^? (n = 1–10) clusters have been systematically investigated by using density functional theory. The optimised geometries show that the structures of [Au_nRb]^? clusters favour the three-dimensional structure at n ≥ 8. The Rb atoms tend to occupy the most highly coordinated position and form the largest probable number of bonds with gold atoms. One Au atom capped on [Au_n-1Rb]^? structures is the dominant growth pattern for n = 2–8 and Rb atom capped on Au_n^? structures for n = 9–10. The averaged atomic bonding energies, fragmentation energies, second-order difference of energies, and highest occupied molecular orbital–lowest unoccupied molecular orbital gaps exhibit a pronounced even–odd alternations phenomenon. The charges in [Au_nRb]^? clusters transfer from the Rb atoms to Au_n host. In addition, it is found that the most favourable dissociation channel of the [Au_nRb]^? clusters is to eject a Rb atom and the highest energy dissociation path is Rb^? anion ejection.     

Copper clusters: electronic effect dominates over geometric effect

A minimal parameter tight binding molecular dynamics scheme is used to study Cu _n clusters with . We present results for relaxed configurations of different symmetries, binding energies, relative stabilities and HOMO-LUMO gap energies for these clusters. Detailed comparison for small clusters n = 3-9 with ab initio and available experimental results shows very good agreement. Even-odd alternation due to electron pairing and magic behaviour for Cu₂, Cu₈, Cu₁₈ and Cu₂₀ due to electronic shell closing are found. We found electronic effects, electronic shell closing and electron pairing in the HOMO dominates over the geometrical effect to determine the relative stability of copper clusters. The present results indicate that tight-binding molecular dynamics scheme can be relied on to provide a useful semiempirical scheme in modeling interactions in metallic systems.Received: 3 May 2004, Published online: 26 October 2004PACS: 36.40.Cg Electronic and magnetic properties of clusters - 36.40.Mr Spectroscopy and geometrical structure of clusters - 36.40.Qv Stability and fragmentation of clusters     

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.     

密度泛函理论研究ScnO(n=1—9)团簇的结构、稳定性与电子性质

采用基于密度泛函理论的BP86/CEP-121G （O原子采用6-311G^**基组）方法,对Sc_nO （n=1—9）团簇的几何结构、能量与稳定性、电子结构性质及其随团簇尺寸的变化趋势进行了研究.随着团簇原子个数的增加,O原子从位于Sc_n团簇结构的边缘转变为占据团簇的内部位置.O原子的掺入增加了Sc_n团簇的稳定性,使其能隙升高,并改变了其稳定性及电子结构性质随团簇尺寸变化的规律;含有偶数个Sc原子的氧化物团簇比其周围邻近的含有奇数个Sc原子的氧化物团簇具有相对较高的稳定性.Sc_nO团簇电离势的理论计算值与实验值符合得较好,而其电子亲和势呈现振荡交替上升的变化趋势;用最大化学硬度规律等方法表征了Sc_nO氧化物团簇的稳定性和电子结构性质. 关键词： nO团簇')" href="#">Sc_nO团簇 几何结构 电子性质 密度泛函理论     

Geometric and electronic structures of AlnCum (n = 5–9, m = 1–3) clusters: genetic algorithm combined with ab initio models

The geometries, stabilities and electronic structures of Al _n Cu _m (n?=?5–9, m?=?1–3) clusters were explored by using the genetic algorithm combined with ab initio methods. The geometric structures are almost spherical when the valence electrons are around the magic number 20, otherwise the structures are oblate or prolate. The stabilities of the clusters are related to both the Cu/Al ratios and the electronic configurations. The clusters with lower Cu/Al ratios have high stabilities. The molecular orbitals are in accord with the shell structures predicted by the jellium model. The 3d orbitals of the Cu atoms are localised, although their orbital energies are between the 1P and 1D jellium orbitals. The Al₆Cu₂ with 20 valence electrons forms closed 1S²1P⁶1D¹⁰2S² shells, and shows large binding energy and removal energy, large ionisation potential and small electron affinity. For the no-magic clusters, the structure deformation leads to crystal-field-like splitting of the degenerate shells and stabilises the clusters.     

碳掺杂硼氮纳米管电子场发射的第一性原理研究

对闭口硼氮纳米管（BNNT）顶层掺碳体系,运用第一性原理研究了电子场发射性能.结果表明,掺碳的BNNT体系电子结构变化显著;外电场愈强,体系态密度向低能端移动幅度愈大,且最高占据分子轨道（HOMO）/最低未占据分子轨道（LUMO）能隙愈小.体系态密度和局域态密度,HOMO和LUMO及其能隙分析一致表明,各种碳掺杂体系中C_eqBNNT的场发射性能最佳. 关键词： 硼氮纳米管 碳掺杂 第一性原理     

Density-functional theory study of structures,stabilities, and electronic properties of the Cu2-doped silicon clusters: Comparison with pure silicon clusters

Equilibrium geometric structures, stabilities, and electronic properties of Si_nCu₂ (n=1–8) clusters and pure silicon Si_n (n=3–10) clusters are investigated systematically by exchange-correlation density functional (B3LYP). The optimized geometries show that the most stable isomers have 3D structure for n=2, 4–8, and Cu-substituted Si_n+2 clusters is dominating growth pattern for the Si_nCu₂ clusters. The calculated averaged binding energies, fragmentation energies, second-order difference of energies, and the HOMO–LUMO gaps show that Si₂Cu₂ and Si₅Cu₂ clusters have enhanced relative stabilities and chemical stability than their neighboring clusters. Electronic properties of Si_nCu₂ (n=1–8) clusters are studied by calculating the natural population analysis and electrostatic potential, where the results show that the two copper atoms always possess positive charge and positive potential surround them. In addition, the VIP, VEA and the chemical hardness (η) are also analyzed and compared.     

A density functional theory study on size-dependent structures, stabilities, and electronic properties of the bimetallic MnAgm (M=Na, Li; n+m ≤ 7) clusters

The equilibrium geometries, relative stabilities, and electronic properties of M_nAg_m (M=Na, Li; n+m≤ 7) as well as pure Ag_n, Na_n, Li_n (n≤ 7) clusters are systematically investigated by means of density functional theory. The optimized geometries reveal that for 2≤ n ≤ 7, there are significant similarities in geometry among pure Ag_n, Na_n, and Li_n clusters, and the transitions from planar to three-dimensional configurations occur at n=7, 7, and 6, respectively. In contrast, the first three-dimensional (3D) structures are observed at n+m=5 for both Na_nAg_m and Li_nAg_m cluters. When n+m ≥ 5, a striking feature is that the trigonal bipyramid becomes the main subunit of Li_nAg_m. Furthermore, dramatic odd-even alternative behaviours are obtained in the fragmentation energies, second-order difference energies, highest occupied and lowest unoccupied molecular orbital energy gaps, and chemical hardness for both pure and doped clusters. The analytic results exhibit that clusters with even electronic configuration (2, 4, 6) possess weakest chemical reactivity and more enhanced stability.     

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.     

CNDO studies of Y-Ba-Cu-O superconductors IV. The oxygen content effect

The dependence of the electronic structure of superconducting YBa₂Cu₃O _y , is investigated using a quasi-relativistic CNDO/1 molecular orbital method. Electronic structures of model clusters [Ba₈Cu₃O _n ] ^q with total chargesq=23–2n forn=11 to 14 in various Cu(1) coordination geometries are compared. The increasing oxygen content causes the electron density transfer from the central Cu(1)O(1,5) _x area to the lateral Cu(2)O(3,4)₂ sheets. The isomerization effects are important for the structures withn=12.     

TinMg (n=1—10)掺杂团簇的密度泛函研究

采用密度泛函(DFT)中的B3LYP方法,选择sto-3g基组,优化并得到了Ti_nMg(n=1—10)小团簇的基态平衡结构,计算出了掺杂团簇的基态结构的平均键长、对称性、原子化能、能级分布、能级间隙、束缚能、总能的二阶差分. 结果表明,随着团簇原子数的增加,镁原子更容易趋于团簇表面位置,镁-钛平均键长大于钛-钛平均键长,以对称性结构为最稳定的基态结构,且呈多个五角双锥结构. 其中Ti₅Mg和Ti₈Mg的结构更为稳定. 关键词： 密度泛函 钛-镁团簇 基态结构     

Theoretical study of small Mo clusters and molecular nitrogen adsorption on Mo clusters

This paper studies the small molybdenum clusters of Mo_n (n=2--8) and their adsorption of N₂ molecule by using the density functional theory (DFT) with the generalized gradient approximation. The optimized structures of Mo_n clusters show the onset of a structural transition from a close-packed structure towards a body-centred cubic structure occurred at n=7. An analysis of adsorption energies suggests that the Mo₂ is of high inertness and Mo₆ cluster is of high activity against the adsorption of N₂. Calculated results indicate that the N₂ molecule prefers end-on mode by forming a linear or quasi-linear structure Mo--N--N, and the adsorption of nitrogen on molybdenum clusters is molecular adsorption with slightly elongated N--N bond. The electron density of highest occupied molecular orbital and lowest unoccupied molecular orbital, and the partial density of states of representative cluster are also used to characterize the adsorption properties of N₂ on the sized Mo_n clusters.     

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.     

Structures,stabilities and electronic properties of boron-doped silicon clusters B3Sin (n=1–17) and their anions

The structures, stabilities and electronic properties of neutral and anionic B₃Si_n (n?=?1–17) clusters have been systemically investigated on the basis of density functional theory at the B3LYP/6-311?+?G(d) level and CALYPSO structure prediction method. The structural searches show that three boron atoms tend to form B₃ triangle encapsulated into Si_n cages with the increasing number of silicon atoms. Most of the lowest energy structures can be derived by using the squashed pentagonal bipyramid structure of B₃Si₄ and B₃Si₄^? as the major building unit. The relative stabilities are studied based on the calculated binding energies, second-order difference of energies and HOMO–LUMO gaps of the lowest energy structures. In addition, Hirshfeld, natural population analysis, Bader approaches and natural electronic configuration are performed to explore the charge transfer. At last, molecular orbital, magnetic properties, IR, Raman and UV–vis spectra are also, respectively, analysed for providing strong support for essential theoretical and experimental research.     

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.     

Density-functional theory study of the geometries,stabilities, and electronic properties of Au n Rb (n = 1–10) clusters: comparison with pure gold clusters

The density functional method with the relativistic effective core potential has been employed to investigate systematically the geometric structures, relative stabilities, growth-pattern behavior, and electronic properties of small bimetallic Au _n Rb (n?=?1–10) and pure gold Au _n (n?≤?11) clusters. For the geometric structures of the Au _n Rb (n?=?1–10) clusters, the dominant growth pattern is for a Rb-substituted Au _{n +1} cluster or one Au atom capped on a Au _{n –1}Rb cluster, and the turnover point from a two-dimensional to a three-dimensional structure occurs at n?=?4. Moreover, the stability of the ground-state structures of these clusters has been examined via an analysis of the average atomic binding energies, fragmentation energies, and the second-order difference of energies as a function of cluster size. The results exhibit a pronounced even–odd alternation phenomenon. The same pronounced even–odd alternations are found for the HOMO–LUMO gap, VIPs, VEAs, and the chemical hardness. In addition, about one electron charge transfers from the Au _n host to the Rb atom in each corresponding Au _n Rb cluster.     

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     

幻数尺寸Li-n-1,Lin,Li+ n+1(n=20,40)团簇的几何结构、电子与光学性质的第一性原理研究

基于密度泛函理论,采用第一性原理分子动力学模拟退火方法,对Li^-_n-1,Li_n,Li⁺_n+1 (n=20,40)的最低能量结构进行了全局搜索. 发现锂团簇的生长模式是以单个或多个嵌套的正多面体为核心,其余原子以五角锥为基本单元围绕核心生长. 基于最低能量结构的第一性原理电子结构计算得到锂团簇的分子轨道能级分布与无结构凝胶模型给出的电子壳层完全一致. 在总电 关键词： 团簇 电子结构 极化率 光吸收