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.     

Subtractive manufacturing with geminal powers:making good use of a bad wave function

The cluster Jastrow antisymmetric geminal power ansatz was recently introduced as a promising approach for treating weak and strong electron correlations simultaneously. One crucial aspect of this ansatz is that the Jastrow operator allows the geminal power to achieve size consistency through the deletion of unphysical ionic terms. Here, we present data suggesting that the effects of such deletions go much deeper, causing the geminal to ‘intentionally’ take on a highly unphysical form that, in the presence of the Jastrow's deletions, nonetheless results in an accurate final wave function, a process that we note is similar to the variation-after-projection approach of projected Hartree–Fock theory. Indeed, in both LiF and N₂, we show that the optimal geminal is quite unphysical if considered on its own, but in ways that the Jastrow easily corrects to yield a highly accurate final wave function.     

Calculation on the CO2 influences on the structure,stability of (MgO)m (m = 1–6) clusters

ABSTRACT

The concentration of carbon dioxide (CO₂) has a significant influence on the morphology of thermal decomposition products of magnesite. So, structures, stabilities and adsorption mechanisms of (MgO)_m (m?=?1–6) clusters by one or two CO₂ molecules were calculated by the GGA-PW91 method. The results show that the stability of the considered clusters is (MgO)_m(CO₂)₂ clusters > (MgO)_m(CO₂) clusters > (MgO)_m clusters by the average binding energy. Certain low-lying isomers of (MgO)_m(CO₂) and (MgO)_m(CO₂)₂ clusters which have an isolated O atom are deviating from the cluster center which possess higher kinetic activity. (MgO)_m clusters prefer to adsorb a CO₂ molecule, while (MgO)₃(CO₂) clusters prefer to adsorb a CO₂ molecule rather than the neighbors. Magnesite is difficult to transit to (MgCO₃)₂ clusters at room temperature. However, magnesite will spontaneously transit to (MgO)₂ clusters and further transit to MgO crystal which need to adsorb more energy at 700?K.     

Multiply ionization of diethyl ether clusters by 532 nm nanosecond laser: The influence of laser intensity and the electron energy distribution

The formation mechanism for multiply charged ions (C^q+ and O^q+ (q = 2–4)) were investigated using a dual polarity time-of-flight mass spectrometer when diethyl ether clusters interacted with nanosecond laser pulse. The signal intensity of multiply charged ions and electron energy was measured experimentally. It was shown that the intensity of multiply charged ions increased about 50 times when laser intensity increased from 7.6 × 10⁹ to 7.0 × 10¹⁰ W/cm², then saturated as laser intensity increased further. It is interesting that the evolution of the mean value of electron energy was same to that of multiply charged ions. The theoretical calculation showed the ionization potential of atomic ions could be significantly decreased due to the effect of Coulomb screening especially at low laser intensity. It indicated that the electron ionization combined with Coulomb screening effect could explain the production of multiply charged ions in nanosecond laser field.     

三核铁簇硫酸盐K_2(H_3O)_3[Fe_3(H_2O)_3O(SO_4)_6]·6H_2O的合成与晶体结构

在室温条件下合成了含三核铁簇的硫酸盐配合物K2(H3O)3[Fe3(H2O)3O(SO4)6].6 H2O,借助IR光谱、紫外-可见吸收光谱、X射线光电子能谱(XPS)和X射线单晶衍射等测试手段对其结构进行了表征.结果表明,标题化合物属于六方晶系,P6(3)/m空间群,晶胞参数为:a=b=0.963 7(2)nm,c=1.885 1(9)nm,V=1.516 3(9)nm3,Z=2,Dc=2.316 g/cm3,GOOF=1.089,R1=0.062 8,wR2=0.165 1.其分子由1个三核铁簇阴离子[Fe3(H2O)3O(SO4)6]5-、2个K+离子、3个水合质子H3O+和6个结晶水分子组成.     

钼钒氧簇二聚体[Ni(enMe)_2]_4{[Ni(enMe)_2][Ni(enMe)_2(H_2O)]_2[Mo_8~(Ⅵ)V_6~(Ⅳ)O_(38)(V~ⅤO_4)]_2}·8H_2O的合成与结构表征(英文)

在水热条件下合成了一例新型的多金属氧酸盐二聚物,[Ni(enMe)2]4{[Ni(enMe)2][Ni(enMe)2(H2O)]2[Mo8ⅥV6ⅣO38(VⅤO4)]2}.8H2O(1)(enMe=1,2-丙二胺),利用元素分析、红外光谱分析、粉末X射线衍射、热重分析和单晶X射线衍射表征了其结构。结果表明,化合物(1)属于单斜晶系,P2(1)/n空间群.晶胞参数为a=1.9685(4)nm,b=1.3549(3)nm,c=2.7039(5)nm,α=90°,β=93.94(3)°,γ=90°,V=7.195(2)nm3,Z=4,Dc=2.390g/cm3,Mr=2588.4,μ=3.195mm-1,F(000)=5012,最终R1=0.0743,wR2=0.1861.与此同时,(1)是第一个具有二帽-Keggin型钼钒氧簇的二聚体,它由过渡金属部分[Ni(enMe)2(H2O)]22+连接形成{[Ni(enMe)2][Ni(enMe)2(H2O)]2[Mo8ⅥV6ⅣO38(VⅤO4)]2}8-二聚阴离子.     

Motif Reconstruction in Clusters and Layers: Benchmarks for the Kawska–Zahn Approach to Model Crystal Formation

A recently developed atomistic simulation scheme for investigating ion aggregation from solution is transferred to the morphogenesis of metal clusters grown from the vapor and layers deposited on a substrate surface. Both systems are chosen as benchmark models for intense motif reorganization during aggregate/layer growth. The applied simulation method does not necessarily involve global energy minimization after each growth event, but instead describes crystal growth as a series of structurally related configurations which may also include local energy minima. Apart from the particularly favorable high‐symmetry configurations known from experiments and global energy minimization, we also demonstrate the investigation of transient structures. In the spirit of Ostwald’s step rule, a continuous evolution of the aggregate/layer structure during crystal growth is observed.     

K2B12F12: A rare A2X structure for an ionic compound at ambient conditions

The anhydrous salt K₂B₁₂F₁₂ crystallized from aqueous solution and its structure was determined by single crystal X-ray diffraction. The Ni₂In-type structure it exhibits is rare for an A₂X ionic compound at 25 °C and 1 atm., consisting of an expanded hexagonal close-packed array of B₁₂F₁₂²⁻ centroids (cent?cent distances: 7.204-8.236 Å) with half of the K⁺ ions filling all of the O_h holes and half of the K⁺ ions filling all of the D_3h trigonal holes in the close-packed layers that are midway between two “empty” T_d holes. The structure is also unusual in that the bond-valence sum for the K⁺ ions in O_h holes is less than or equal to 0.73 (the bond-valence sum for the other type of K⁺ ion is 1.16). A variation of the Ni₂In structure is exhibited by the previously published monohydrate Cs₂(H₂O)B₁₂F₁₂, for which an improved structure is also reported here. For K₂B₁₂F₁₂: monoclinic, C2/c, a = 8.2072(8), b = 14.2818(7), c = 11.3441(9) Å, β = 92.832(5)°, Z = 4, T = 120(2) K. For Cs₂(H₂O)B₁₂F₁₂: orthorhombic, P2₁2₁2₁, a = 9.7475(4), b = 10.2579(4), c = 15.0549(5) Å, Z = 4, T = 110(1) K.     

配体稳定的二元过渡金属团簇[PdAu8(PR3)8]2＋(R＝Me, OMe, H, F, Cl, CN)的量子化学理论研究

采用从头计算MP2方法和密度泛函理论方法, 对过渡金属团簇[PdAu₈(PR₃)₈]^2＋(R＝Me, OMe, H, F, Cl, CN)的几何结构、电子结构以及团簇各组成部分之间的结合能进行了研究. MP2方法和SVWN局域泛函能够对团簇的结构给予准确的描述, 而离域泛函BP86, PBE, BLYP和杂化泛函B3LYP则过高地估计了团簇的几何结构参数. 电子结构研究表明Pd, Au原子通过 d电子的成键作用构成团簇内核[PdAu₈]^2＋, [PdAu₈]^2＋与PR₃配体则通过“σ给予/π反馈”模式成键. PR₃配体与[PdAu₈]^2＋的结合能够加强Pd-Au之间的成键作用, 增大前线轨道能级间隙, 从而提高团簇的稳定性. PR₃配体中R基团供、吸电能力的变化对[PdAu₈(PR₃)₈]^2＋结构的影响较小, 但对[PdAu₈]^2＋-PR₃结合能的影响较大. 能量分析显示不同PR₃与[PdAu₈]^2＋之间具有相近的轨道作用能, 与R基团供、吸电能力相关的非轨道作用能成为影响两者连接牢固程度的决定因素.     

包含两个平面五配位碳原子C2＋nB10－n (n＝0～10)团簇的结构的理论研究

采用B3LYP/6-311＋G**方法, 我们优化了初始构型中包含两个平面五配位碳原子(ppCs)的C_{2＋nB10－n (n＝0～10)团簇的结构并计算了它们的振动频率. 计算结果表明, C2＋nB10－n (n＝0～2)团簇是稳定的, 而且这三个结构中ppC—B键的Wiberg键级介于0.511～0.909之间, ppC—C键的Wiberg键级为0.2254 (n＝1)和0.8586 (n＝2), ppC的键级介于3.778到3.879之间, 即这三个结构中存在两个ppCs, 而且ppC遵循八隅规则; C2＋nB10－n (n＝3～6)团簇的最稳定结构包含一个ppC; C2＋nB10－n (n＞6)团簇能量最低结构中不存在ppC. 而且只有团簇C2＋nB10－n (n＝0～2)中没有悬键, 它们的(电子数分别为: 6, 7和8, 计算它们的NICS(0)值表明强芳香性一般位于局部的三元环中心, 表明局部离域有利于平面结构的形成. C2＋nB10－n (n＝0～2)团簇的第一垂直激发能分别为: 1.91, 0.56和3.12 eV.}