Structural, electronic, and magnetic properties of boron cluster anions doped with aluminum: BnAl- (2≤n≤9)

The geometrical structures, relative stabilities, electronic and magnetic properties of small B n Al (2 ≤ n ≤ 9) clusters are systematically investigated by using the first-principles density functional theory. The results show that the Al atom prefers to reside either on the outer-side or above the surface, but not in the centre of the clusters in all of the most stable B n Al (2 ≤ n ≤ 9) isomers and the one excess electron is strong enough to modify the geometries of some specific sizes of the neutral clusters. All the results of the analysis for the fragmentation energies, the second-order difference of energies, and the highest occupied-lowest unoccupied molecular orbital energy gaps show that B 4 Al and B 8 Al clusters each have a higher relative stability. Especially, the B 8 Al cluster has the most enhanced chemical stability. Furthermore, both the local magnetic moments and the total magnetic moments display a pronounced odd-even oscillation with the number of boron atoms, and the magnetic effects arise mainly from the boron atoms except for the B 7 Al and B 9 Al clusters.     

Structures and electronic properties of Mo2nNn（n=1-5）:a density functional study

The lowest-energy structures and the electronic properties of Mo2nNn(n=1-5) clusters have been studied by using the density functional theory(DFT) simulating package DMol 3 in the generalized gradient approximation(GGA).The resulting equilibrium geometries show that the lowest-energy structures are dominated by central cores which correspond to the ground states of Mo n(n = 2,4,6,8,10) clusters and nitrogen atoms which surround these cores.The average binding energy,the adiabatic electron affinity(AEA),the vertical electron affinity(VEA),the adiabatic ionization potential(AIP) and the vertical ionization potential(VIP) of Mo2nNn(n=1-5) clusters have been estimated.The HOMO-LUMO gaps reveal that the clusters have strong chemical activities.An analysis of Mulliken charge distribution shows that charge-transfer moves from Mo atoms to N atoms and increases with cluster size.     

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.     

Density Functional Study of Cationic and Anionic Ag_mCu_n (m + n ≤ 5) Clusters

The structural and energetic properties of bimetallic Ag m Cu n clusters (m + n ≤ 5) in the cationic and anionic charged states have been investigated by density functional theory with relativistic effective core potentails.The stable cationic pentamers have three-dimensional structures in contrast to anionic clusters assume planar structures.For the given cluster size the electron affinities decrease as the Cu content increases,while no clear trend can be found in adiabatic ionization potentials.The binding energy per atom also increases with the increasing Cu content and follows the order anion cation.The most probable dissociation channels of the clusters considered are also discussed.     

Structural and bonding properties of ScSi_n~-(n=2～6) clusters:photoelectron spectroscopy and density functional calculations

Anion ion photoelectron spectroscopy and density functional theory (DFT) are used to investigate the electronic and structural properties of ScSi_n^- (n=2sim6) clusters and their neutrals. We find that the structures of ScSi_n^- are similar to those of Si_n+1^-. The most stable isomers of ScSi_n^- cluster anions and their neutrals are similar for n=2, 3 and 5 but different for n=4 and 6, indicating that the charge effect on geometry is size dependent for small scandium-silicon clusters. The low electron binding energy (EBE) tails observed in the spectra of ScSi_4,6^- can be explained by the existence of less stable isomers. A comparison between ScSi_n^- and VSi_n^- clusters shows the effects of metal size and electron configuration on cluster geometries.     

Density functional calculations on 13-atom Pd12M （M= Sc-Ni） bimetallic clusters

The geometric structures,electronic and magnetic properties of the 3d transition metal doped clusters Pd12M(M=Sc-Ni) are studied using the semi-core pseudopots density functional theory.The groundstate geometric structure of the Pd12M cluster is probably of pseudoicosahedron.The Ih-Pd12M cluster has the most thermodynamic stability in five different symmetric isomers.The energy gap shows that Pd12M cluster is partly metallic.Both the absolutely predominant metal bond and very weak covalent bond might exist in the Pd12M cluster.The magnetic moment of Pd12M varies from 0 to 5 μB,implying that it has a potential application in new nanomaterials with tunable magnetic properties.     

Structural evolutions and electronic properties of Au_nGd(n=6–15) small clusters: A first principles study

Structural, electronic, and magnetic properties of Au_nGd(n = 6–15) small clusters are investigated by using first principles spin polarized calculations and combining with the ab-initio evolutionary structure simulations. The calculated binding energies indicate that after doping a Gd atom Aun Gd cluster is obviously more stable than a pure Au_(n+1) cluster.Au_6Gd with the quasiplanar structure has a largest magnetic moment of 7.421 μ_B. The Gd-4 f electrons play an important role in determining the high magnetic moments of Au_nGd clusters, but in Au_6Gd and Au_(12) Gd clusters the unignorable spin polarized effects from the Au-6 s and Au-5 d electrons further enhance their magnetism. The HOMO–LUMO(here, HOMO and LUMO stand for the highest occupied molecular orbital, and the lowest unoccupied molecular orbital, respectively)energy gaps of Au_nGd clusters are smaller than those of pure Au_(n+1) clusters, indicating that Au_nGd clusters have potential as new catalysts with enhanced reactivity.     

First-principles influence of study of GaTAs7 multi-charge on ionic cluster and its structure

This paper investigates the structures and stabilities of neutral GaTAs7 cluster and its ions in detail by using first-principles density functional theory. Many low energy structures of GaTAs7 cluster are found. It confirms that the ground state structure of neutral GaTAs7 cluster is a pentagonal prism with four face atoms like a basket structure, as reported by previous works. The ground state structures of positive Ga7As7 cluster ions are different from that of the neutral cluster. These investigations suggest that Ga atoms occupy the capping positions more easily than As atoms. Mulliken population analyses also show that Ga atoms can lose or obtain charge more easily than As atoms. It finds that the neutral GaTAs7 cluster can become more stable by gaining one or two additional electrons but further more electrons would cause the decrease of binding energy. The ionisation energy increases with the increase of the number of the removed electrons. These calculated results indicate that the net magnetic moment of the neutral GaTAs7 cluster is zero because all electrons axe paired together in their respective moleculax orbits. But for the ionic GaTAs7 cluster with odd number of electrons, the net magnetic moment is 1.0 μB due to an unpaired electron.     

First-Principles Study of Geometries,Stabilities and Electronic Properties of Ca2Sin （n=1-11） Clusters

The equilibrium geometries, relative stabilities, and electronic properties of Ca2Sin （n = 1-11） clusters have been systematically investigated by using the density function theory at the 6-311G （d） level The optimized geometries indicate that the most stable isomers have three-dimensional structures for n = 3-11. The electronic properties of Ca2 Sin （n = 1-11） dusters axe obtained through the analysis of the natural charge population, natural electron configuration, vertical ionization potential, and vertical electron affinity. The results show that the charges in corresponding Ca2Sin clusters transfer from the Ca atoms to the Sin host. Based on the obtained lowest-energy geometries, the size dependence of cluster properties, such as averaged binding energies, fragmentation energies, second-order energy differences, HOMO- LUMO gaps and chemical hardness, are deeply discussed.     

The relativistic density functional investigations on geometries, electronic and magnetic properties of Irn (n=1-13) clusters

<正>The Ir_n(n=1-13) clusters are studied using the relativistic density functional method with generalized gradient approximation.A series of low-lying structures with different spin multiplicities have been considered.It is found that all the lowest-energy Ir_n(n=4-13) geometries prefer non-compact structures rather than compact structure growth pattern.And the cube structure is a very stable cell for the lowest-energy Ir_n(n8) clusters.The second-order difference of energy,the vertical ionization potentials,the electron affinities and the atomic average magnetic moments for the lowest-energy Ir_n geometries all show odd-even alternative behaviours.     

中性和阳离子丁酮团簇的结构及稳定性的理论研究

使用密度泛函B3LYP方法,在6-31G*和6-311+G**基组水平上计算中性和阳离子丁酮团簇(CH_3COC_2H_5)_n和(CH_3COC_2H_5)_n~+(n 7)的稳定结构,并比较不同尺寸团簇之间的相对稳定性.中性和阳离子丁酮团簇的结构具有相似性:n=3—7时,组成团簇的丁酮的平均几何参数基本相同,单环结构最稳定;随着团簇尺寸的增加,双环结构的稳定性逐渐上升.通过平均结合能、一阶差分能、HOMO-LUMO能隙等计算分析可知:在所研究的各种尺寸团簇中,(CH_3COC_2H_5)_3是最稳定的中性团簇,与实验中的最强峰对应;(CH_3COC_2H_5)_4~+是最稳定的阳离子团簇.通过电离能计算得到丁酮分子的垂直电离能为9.535 eV与实验值相符,同时证明中性和阳离子丁酮二元团簇的结构变化较大.研究结果为实验中丁酮团簇碎片离子的形成机理提供一定的理论依据,并且为进一步研究酮类分子团簇的生长规律提供有价值的信息.     

中等光强纳秒激光电离苯团簇产生多价碳离子的数值模拟和实验研究

飞秒强激光与团簇相互作用产生多价离子的现象已被广泛报道,然而近期多个研究小组发现当功率密度低至1010W/cm2的纳秒激光照射团簇时,同样也观察到了多价离子的存在.虽然可以用"多光子电离引发-逆韧致吸收加热-电子碰撞电离"电离机理对这种现象进行解释,但是缺乏相应的数值模拟.建立了一个简化的数值模型,根据有质动力势Up计算团簇内电子能量,再由Lotz公式计算出相应的电离截面,最后由动力学反应速率方程计算出团簇内多价碳离子随时间的演变.详细分析了团簇尺寸、电子密度等关键参数对多价离子产生的影响.数值模拟结果表明:团簇电离在小于0.7 ns时间尺度内完成,C2+,C3+和C4+多价离子强度达到平衡后,离子相对强度由大到小依次为C2+,C3+,C4+,这与实验结果相一致;多价离子的价态随着团簇尺寸的增加而升高,半径为5.6 nm的苯团簇比半径为3 nm的苯团簇更容易产生高价态的离子,这也与实验结果相一致.     

Ti$lt;sub$gt;2$lt;/sub$gt;B$lt;sub$gt;$lt;i$gt;n$lt;/i$gt;$lt;/sub$gt;($lt;i$gt;n$lt;/i$gt;=1–10)团簇的结构与稳定性:基于从头算的研究

采用密度泛函理论中的B3LYP方法, 结合从头算的CCSD(T)方法对Ti₂B_n(n=1–10)团簇的稳定性和电子性质进行了研究. 发现两个Ti原子的掺杂导致B_n团簇结构发生了根本性变化. 随着n的增大, Ti₂B_n团簇结构生长非常规律. 所有的最稳定结构都可看成双锥结构, 并且两个Ti原子处在双锥结构的锥顶. 根据二阶差分能量分析, 得出Ti₂B_n(n=1–10)团簇的幻数是6, 7和8. 进一步分析了团簇的Ti原子解离能、B原子解离能以及团簇的电子亲和势和电离势. 这些能量分析表明Ti₂B₆团簇既有良好的热力学稳定性, 又有良好的动力学稳定性. 应用前线轨道理论, 对Ti原子与B₆之间的成键进行了分析, 了解其稳定性的根源. 关键词： 2B_n团簇')" href="#">Ti₂B_n团簇 稳定性 从头计算 电子结构     

InC_n~+(n=1-10)团簇的密度泛函理论研究

利用密度泛函理论的B3LYP方法,在LANL2DZ水平上对碳基混合团簇InC_n~+(n=1—10)进行了系统研究,得到了这个团簇体系的最稳定几何构型以及基态结构的电子态、最低振动频率、总能量、自旋污染期望值、偶极距、转动常数等.计算结果显示:团簇的最稳定结构是In原子位于碳链末端的直线型构型;n为偶数的基态是三重态,除InC~+外,n为奇数的基态是单态.通过对增量结合能和能量二阶差分的计算和分析可以得出,随着团簇尺寸的增加,团簇的稳定性表现出强烈的奇强偶弱振荡规律.电离能的计算结果进一步证实了这种振荡规律的正确性.对系列团簇基态的磁性研究表明,团簇的磁矩随团簇尺寸的增加呈现出明显的奇弱偶强振荡规律.极化率的计算结果显示,极化率张量的平均值及各向异性不变量都随着团簇尺寸的增大而增大.     

CH_3I~(2+)的二体、三体解离过程的理论研究

采用密度泛函和耦合簇理论从过渡态的观点对CH_3I~(2+)离子的解离过程进行了计算和分析.优化得到了CH_3I,CH_3I+和CH_3I~(2+)的稳定结构及解离过渡态的几何构型并给出了相应能量,计算的第一、二电离能与实验结果符合.基于母体离子、过渡态和解离碎片的几何结构和能量,对CH_3I~(2+)的两体解离过程和三体解离过程进行了详细分析和讨论.给出了二体、三体解离的可能解离通道,并分析了实验上观测到的解离碎片离子的产生机制.计算结果表明,三重和单重绝热势能面上的一些解离过程表现出明显的差异.     

Ni掺杂对Cu团簇结构稳定性的影响

采用密度泛函理论对Cu_n和Cu_n-1Ni(n=3-14)团簇的结构及稳定性进行研究.结果证明Cu_n(n=3-14)团簇的基态不是密实结构而是类似双平面的构型;计算表明:Ni掺杂增加了铜团簇的稳定性,Cu_nNi(n=2-13)团簇的最稳态结构与单质铜团簇不同而是以形成二十面体为基础的密实结构,Ni原子趋于和尽量多的Cu原子成键而最终陷入笼状团簇的中心;偶数个粒子的团簇具有相对高的稳定性,尤其Cu₃Ni,Cu₇Ni和Cu₉Ni;陷入笼状团簇内部的Ni原子带正电,使得位于表面的Cu原子带负电,从而增加了由这种团簇构成的材料的化学稳定性,如耐腐蚀性等.     

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.     

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采用Langmuir探针法结合发射光谱法对螺旋波诱导的低压氢等离子体进行诊断,根据Druyvesteyn 方法和日冕模型分析电子能量几率函数(EEPF)、有效电子温度(Teff)、电子密度(ne)及激发态氢原子密度(nH*)随实验参数的变化规律.结果表明:随射频功率(Prf)、气压(p)和约束磁场(B)的增大,EEPF峰位由高能向低能移动,Teff 下降;当Prf从25W增大至35W左右时,ne发生跳跃增长,而nH*始终随Prf增大线性增长;随p增大,ne和nH*都呈现先增加后减小的变化规律;随B增强,ne线性增长,而nH*先增大后减小.