Electronic Structure and Stability of Bulky Mercury Clusters

The potential energy surface (PES) of bulky mercury clusters with n = 4-6 (n is the number of atoms) was studied in the framework of the MNDO method. It is shown that the bonding character of the highest occupied molecular orbital is one of the conditions providing the relative stability of such systems. The possibility of generating this electronic structure of a cluster nucleus is discussed. The effect of atomic bonding in the cluster on the stability of the molecular systems under study is examined.     

(BN)_n团簇的结构和稳定性

用HF方法、密度泛函理论的B3LYP以及微扰理论的MP2方法 ,在 6 3 1G(d)基组水平上 ,对 (BN) n(n =1～ 16)团簇的各种可能结构进行了优化 .讨论了环状与笼状稳定团簇的几何构型、自然键轨道 (NBO)、振动频率、结合能、核独立化学位移 (NICS)和能量二次差分 ,得到了 (BN) n(n =1～ 16)团簇结构的稳定性信息 .比较了HF ,B3LYP以及MP2三种理论方法对(BN) n 团簇的适应性所表现出的差异 .     

AlnO2团簇结构和稳定性的量子化学研究

采用密度泛函理论（DFT）的B3LYP方法,在6-311G＊＊水平上对AlnO2（n=1～10）团簇的几何和电子结构进行了理论计算.讨论了混合团簇的基态结构与振动频率,以及电荷转移与成键特征.结果表明,富氧的AlO2基态结构是以Al原子为核心的线状结构,双聚体和富铝的AlnO2基态结构是以2个O原子为中心的AlmO（m...     

Structure and Stability of (NG)nCN3Be3+ Clusters and Comparison with (NG)BeY0/+

The noble gas binding ability of CN₃Be₃⁺ clusters was assessed both by ab intio and density functional studies. The global minimum structure of the CN₃Be₃⁺ cluster binds with four noble‐gas (NG) atoms, in which the Be atoms are acting as active centers. The electron transfer from the noble gas to the Be atom plays a key role in binding. The dissociation energy of the Be? NG bond gradually increases from He to Rn, maintaining the periodic trend. The HOMO–LUMO gap, an indicator for stability, gives additional insight into these NG‐bound clusters. The temperature at which the NG‐binding process is thermodynamically feasible was identified. In addition, we investigated the stability of two new neutral NG compounds, (NG)BeSe and (NG)BeTe, and found them to be suitable candidates to be detected experimentally such as (NG)BeO and (NG)BeS. The dissociation energies of the Be? NG bond in monocationic analogues of (NG)BeY (Y=O, S, Se, Te) were found to be larger than in the corresponding neutral counter‐parts. Finally, the higher the positive charge on the Be atoms, the higher the dissociation energy for the Be? NG bond becomes.     

AlmN2和AlmN+2(m=1～8)团簇结构与稳定性的量子化学研究

用密度泛函理论(DFT）的B3LYP方法，在6-311G水平上AlmN2和AlmN^ 2(m=1～8)团簇的几何构型、电子结构、振动频率和分子轨道进行了理论研究．结果表明，AlmN2类团簇的基态结构有两种基本构型，一种是以N-N键为核心周围与Al原子相配位形成的，一种是由两个AlnN(n≤m，2)分子碎片通过共用Al原子或Al—Al键相互结合形成的．对AlnN分子碎片相互结合形成结构的绝热电离能讨论得到，m为偶数的团簇比m为奇数的稳定。     

Structure of the Li + Ion Close Environment in Various Solvents

The literature data on various methods for studying structural characteristics of the Li+ ion close environment in a number of oxygen-containing solvents were generalized. The coordination numbers of the Li+ cation, interparticle distances, and types of ionic association were discussed. The number of coordinated solvent molecules and the Li+–O distance in the first coordination shell are independent of the nature of the considered solvents.     

Stability of Noble‐Gas‐Bound SiH3+ Clusters

The stability of noble gas (Ng)‐bound SiH₃⁺ clusters is explored by ab initio computations. Owing to a high positive charge (+1.53 e^?), the Si center of SiH₃⁺ can bind two Ng atoms. However, the Si?Ng dissociation energy for the first Ng atom is considerably larger than that for the second one. As we go down group 18, the dissociation energy gradually increases, and the largest value is observed for the case of Rn. For NgSiH₃⁺ clusters, the Ar–Rn dissociation processes are endergonic at room temperature. For He and Ne, a much lower temperature is required for it to be viable. The formation of Ng₂SiH₃⁺ clusters is also feasible, particularly for the heavier members and at low temperature. To shed light on the nature of Si?Ng bonding, natural population analysis, Wiberg bond indices computations, electron‐density analysis, and energy‐decomposition analysis were performed. Electron transfer from the Ng centers to the electropositive Si center occurs only to a small extent for the lighter Ng atoms and to a somewhat greater extent for the heavier analogues. The Si?Xe/Rn bonds can be termed covalent bonds, whereas the Si?He/Ne bonds are noncovalent. The Si?Ar/Kr bonds possess some degree of covalent character, as they are borderline cases. Contributions from polarization and charge transfer and exchange are key terms in forming Si?Ng bonds. We also studied the effect of substituting the H atoms of SiH₃⁺ by halide groups (?X) on the Ng binding ability. SiF₃⁺ showed enhanced Ng binding ability, whereas SiCl₃⁺ and SiBr₃⁺ showed a lower ability to bind Ng than SiH₃⁺. A compromise originates from the dual play of the inductive effect of the ?X groups and X→Si π backbonding (p_z–p_z interaction).     

ChemInform Abstract: Origin of the Unusual Stability of B12 and B13+ Clusters.

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.     

Growth Ability and Stability Indices of Clusters

Electronegativity and hardness are well known electronic concepts that help to interpret the electronic rearrangements of atoms in molecules. Parallel atomic concepts can be established that help to understand the growth processes occurring in cluster formation experiments. Those, which are called here the growth ability and the stability index, are essentially the first and second derivatives of the cluster binding energy with respect to the number of atoms, respectively. The first one has not been used before, and by application to transition metal clusters we show that a consideration of both indices helps to interpret the observed cluster mass spectra.     

Theoretical Study of Structure and Stability of B n O and B n O2 Clusters

The structures and stabilities of B _n O and B _n O₂ clusters with n ≤ 6 are studied systematically by using density-functional theory. The lowest-energy structures of B _n O clusters favor two-dimensional, and can be obtained from B _n or B _n−1O. For B _n O₂, unexpectedly, all of the most stable B _n O₂ clusters but B₆O₂ are linear. Furthermore, in B _n O₂ clusters, the longer the distance between two O atoms, the more stable the structure. To investigate the relative stability of considered clusters, binding energies per atom, reaction energies, and fragmentation energies are also calculated and discussed.     

CnAl2（n=1-10）团簇的结构特征与稳定性

采用密度泛函理论(DFT)的B3LYP方法,在6-311G*水平上对CnAl2(n=1-10)团簇的几何构型和电子结构进行了结构优化和振动频率计算.结果表明,富铝的CAl2团簇基态结构为折线型面状结构,多碳和双聚体的CnAl2团簇基态结构均为Al原子端基配位的线状结构.通过对基态结构的能量分析,得到了n为偶数的CnAl2团簇比n为奇数稳定的结论.     

Atoms-in-molecules treatment of Li 2 + and Li2 using optimum Gaussian approximations of Li+ and Li eigenstates

Expectation energies for the Li⁺, Li and Li^– ground states and for the 1s ²2p Li excited state are individually minimized with respect to variation of parameters in Gaussian lobe expansions of the 1s, 2s and 2p AO's. A new technique is used to control 1s–2s orthonormality. The resulting approximate many-electron atomic eigen-functions are utilized for determining interatomic matrix elements in atoms-in-molecules (AIM) calculations on the two lowest energy ¹ _g ⁺ states of Li₂ and on the lowest energy ² _g ⁺ and ² _u ⁺ states of Li ₂ ⁺ . For R greater than 4 a.u., convergence to exact theoretical AIM limits, within about 0.001 h.u., is obtained by using three-term expansions. Three-structure Li₂ and two-structure Li ₂ ⁺ AIM energies are above experimental by 0.005 and 0.007 h.u., respectively. It is conjectured that an AIM model extended to permit scaling of valence electrons independently of innershell electrons would reduce significantly these energy differences.

---

Zusammenfassung Die Energieerwartungswerte für die Grundzustände von Li⁺, Li und Li^–1 sowie für den angeregten Zustand 1s² 2p von Li werden einzeln bezüglich der Variationsparameter einer Entwicklung der 1s-, 2s- und 2p-Atomorbitale nach Gaußfunktionen minimisiert. Zur Kontrolle der Orthonormalität der 1s- und der 2s-Funktion wird eine neue Technik angewandt. Die resultierenden angenäherten Atomeigenfunktionen werden bei Atom-in-Molekül (AIM)-Rechnungen für die zwei niedrigsten ¹ _g ⁺ -Zustände von Li₂ und die niedrigsten Zustände der Symmetrie ² _g ⁺ und ² _u ⁺ von Li ₂ ⁺ verwendet. Für einen Atomabstand R größer als 4 A.E. wird mit einer Entwicklung mit drei Termen eine Annäherung bis zu 0,001 A.E. an den exakten theoretischen AIM-Grenzwert erreicht. Die AIM-Energiewerte, die mit drei Resonanzstrukturen von Li₂ bzw. zwei Resonanzstrukturen von Li ₂ ⁺ erhalten werden, liegen 0,005 A.E. bzw. 0,007 A.E. über den experimentellen Werten. Es wird angenommen, daß eine Erweiterung des AIM-Modells, bei der eine Skalierung der Valenzelektronenfunktionen unabhängig von den inneren Elektronen möglich ist, diese Energiedifferenz stark herabsetzen würde.

---

Résumé Les énergies de l'état fondamental de Li⁺, Li et Li^–, et de l'état excité 1s²2p de Li sont individuellement minimisées par rapport à la variation des paramètres dans le développement gaussien des orbitales atomiques 1s, 2s et 2p. Une technique nouvelle est utilisée pour contrler l'orthonormalité 1s–2s. Les fonctions d'onde polyélectroniques approchées résultantes sont utilisées pour des calculs du type atomes dans les molécules (ADM) pour les deux états ¹ _g ⁺ de plus basse énergie de Li₂ et sur les états ² _g ⁺ et ² _g ⁺ de plus basse énergie de Li₂. Pour R supérieur à 4 u.a., la convergence vers les limites théoriques exactes ADM est obtenue avec un développement à trois termes, à 0,001 u.a. près. Les énergies ADM à trois structures pour Li2 et á deux structures pour Li2 sont respectivement á 0,005 et 0,007 a.u. au dessus des énergies expérimentales. On émet l'hypothése qu'un modéle ADM étendu pour permettre le calibrage des électrons de valence indépendamment des électrons des couches internes réduirait d'une manière significative ces différences d'énergie.

---

---

Supported in part by National Science Foundation Grant GP 25415     

Theoretical Study on the Structure and Stability of Si4X（X=Li, Be, B, C, N, O, F） Clusters

1 INTRODUCTION Silicon is an important kind of semiconductormaterial having been used to produce many sorts ofapparatus, digital and linear integrated circuit andLarge Scale Integrated circuit (LSI), and its clustershave drawn many scientists’ atten…     

Relative Stability of Linear Zn Clusters

The MNDO method was used to study the potential energy surface for Zn$_n and Zn_nX_m (n = 2 – 4) linear zinc clusters with terminal and lateral coordinations of the X acceptor groups. The results agree with the formerly proposed hypothesis on the modes of Hg cluster stabilization. Possible effects of the individual properties of the element and the value of the acceptor strength of the ligands on the relative stability of the clusters are discussed.     

AlmN(m=2～9)团簇结构与稳定性的DFT研究

用密度泛涵理论 (DFT)的 B3LYP方法在 6-31G水平上对 AlmN(m=2～ 9)团簇的几何构型、电子结构、振动频率等性质进行了理论研究.给出了以 Alm团簇作为设计 AlmN类结构的母体,考虑在不同位置上结合 N原子的结构,可以较快找到 AlmN类团簇基态结构的一种方法.通过对基态结构的几何参数分析发现, m< 4的结构只存在 Al- N键; m≥ 4的结构 , Al- N键和 Al- Al键共存.对基态结构的绝热电离能讨论结果表明,只存在 Al- N键的 Al2N和 Al3N团簇较稳定.     

Interaction of Triatomic Germanium with Lithium Atoms: Electronic Structure and Stability of Ge3Lin Clusters

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF.     

Sn_nSm(n=1～9)团簇结构稳定性与磁学性质的理论研究

采用Saunders全局优化随机踢球模型与密度泛函理论相结合的方法,在B3LYP/SDD理论水平下研究了锡基原子团簇Sn_n(n=2~10)及锡基稀土原子钐掺杂团簇Sn_nSm(n=1~9)的几何结构、稳定性、电子性质和磁性.结果表明,团簇Sn_nSm(n=1~9)中掺杂的钐原子通常位于主团簇的表面,掺杂团簇的基态结构更倾向于具有较高对称性的三维结构;二元锡基混合团簇的平均结合能变大,稳定性增强,这主要归因于Sn—Sm键比Sn—Sn键的键能大,具有更强的相互作用;掺杂团簇具有较高的磁性,其总磁矩主要源自于钐原子4f电子的贡献;随着团簇尺寸的增加,二元团簇的总磁矩呈现出趋于饱和的现象.