(BN)n(n≤12)团簇的结构及成键性质

利用遗传算法和Gastreich提出的经验势函数研究了(BN)_n(n≤12)团簇的可能稳定结构, 并对能量较低的异构体在HF/6-31G(d)水平进行优化, 得到了(BN)_n(n≤12)团簇的线状、蒲扇形、单环、双环、三环和笼状结构, 讨论了各种结构的特征及相对稳定性. 分析了BN团簇中原子的成键性质, 在单环结构中, N原子以sp2杂化成键, B原子以sp杂化成键, 而在节点处B原子以sp2杂化成键. (BN)6是唯一没有张力的单环结构.     

(XY)12(X=B,Al;Y=P)团簇的结构与稳定性

采用B3LYP／6031G*方法,对(XY)12(X=B,Al;Y=P)笼状团簇的同分异构体进行优化,筛选出能量最低的构型．讨论它们的几何构型、HOMO-LUMO能隙、生成焓、核独立化学位移(NICS)和自由能．得到(BP)12和(AlP)12团簇的最稳定构型均为具有Th对称性的四、六元环组成的笼,亚稳态结构中含有五元环。     

Electronic and structural investigations of gold clusters doped with copper: Aun-1Cu- (n=13-19)

We have obtained the ground state and the equilibrium geometries of Au(n) (-) and Au(n-1)Cu(-) in the size range of n=13-19. We have used first principles density functional theory within plane wave and Gaussian basis set methods. For each of the cluster we have obtained at least 100 distinct isomers. The anions of gold clusters undergo two structural transformations, the first one from flat cage to hollow cage and the second one from hollow cage to pyramidal structure. The Cu doped clusters do not show any flat cage structures as the ground state. The copper doped systems evolve from a general 3D structure to hollow cage with Cu trapped inside the cage at n=16 and then to pyramidal structure at n=19. The introduction of copper atom enhances the binding energy per atom as compared to gold cluster anions.     

离子簇合物N+2Hen(n=1,2,3)的ab initio研究

利用Ｇａｕｓｓｉａｎ９２量子化学从头算程序，选择ＵＭＰ２／６－３１１Ｇ方法，对Ｎ＾＋２Ｈｅ，Ｎ＾＋２Ｈｅ２和Ｎ＾＋２Ｈｅ３等离子簇合物进行了几何优化，并通过频率分析确认了体系的稳定构型。     

Li修饰B12N12储氢行为的密度泛函理论研究

采用基于密度泛函理论(DFT)的第一性原理投影缀加波方法, 研究了Li 修饰的B₁₂N₁₂笼子的储氢行为.计算结果表明: Li 原子吸附在B₁₂N₁₂笼子的四元环和六元环相交的B－N桥位上, 相对于其它六个高对称吸附位置更稳定, B₁₂N₁₂笼子周围最多可以吸附3 个Li 原子, 最稳定的构型是三个Li 原子同时吸附在N原子顶位(Top-N site). 每个Li 原子的周围能吸附三个氢分子, 笼子外侧还可以吸附两个氢分子, 内部最多可以吸附5 个氢分子. 考虑到笼内和笼外的吸附, B₁₂N₁₂笼子总的储氢量(氢分子)达到9.1% (w).     

N60的量子化学研究

C60的发现及其广泛研究促使人们去探索合成其它元素的笼形化合物，特别是氮笼分子，被认为具有较高的热值，是潜在的高能密度材料（HEDM）］，尤其是将其作为火箭推进剂时，可通过自身的分解释放能量，并产生叱，不需要携带供氧物质，这对火箭推进剂的研制将带来根本性的变革，因此倍受人们重视．日本曾在“老任新阁”中简单地提到他们对N。。进行了计算，得到的构型是有几个向内凹陷的宪状体，但对具体的计算结果尚未见报道．本文报道了N60的计算方法及结果．1计算方法计算系采用Turbomole程序，在SGI／ONYXI作站上进行．利用HF从…     

Geometries, stabilities, and electronic properties of different-sized ZrSi(n) (n=1-16) clusters: a density-functional investigation

The ZrSi(n) (n=1-16) clusters with different spin configurations have been systematically investigated by using the density-functional approach. The total energies, equilibrium geometries, growth-pattern mechanisms, natural population analysis, etc., are discussed. The equilibrium structures of different-sized ZrSi(n) clusters can be determined by two evolution patterns. Theoretical results indicate that the most stable ZrSi(n) (n=1-7) geometries, except ZrSi3, keep the analogous frameworks as the lowest-energy or the second lowest-energy Si(n+1) clusters. However, for large ZrSi(n) (n=8-16) clusters, Zr atom obviously disturbs the framework of silicon clusters, and the localized position of the transition-metal (TM) Zr atom gradually varies from the surface insertion site to the concave site of the open silicon cage and to the encapsulated site of the sealed silicon cage. It should be mentioned that the lowest-energy sandwich-like ZrSi12 geometry is not a sealed structure and appears irregular as compared with other TM@Si12 (TM = Re,Ni). The growth patterns of ZrSi(n) (n=1-16) clusters are concerned showing the Zr-encapsulated structures as the favorable geometries. In addition, the calculated fragmentation energies of the ZrSi(n) (n=1-16) clusters manifest that the magic numbers of stabilities are 6, 8, 10, 14, and 16, and that the fullerene-like ZrSi16 is the most stable structure, which is in good agreement with the calculated atomic binding energies of ZrSi(n) (n=8-16) and with available experimental and theoretical results. Natural population analysis shows that the natural charge population of Zr atom in the most stable ZrSi(n) (n=1-16) structures exactly varies from positive to negative at the critical-sized ZrSi8 cluster; furthermore, the charge distribution around the Zr atom appears clearly covalent in character for the small- or middle-sized clusters and metallic in character for the large-sized clusters. Finally, the properties of frontier orbitals and polarizabilities of ZrSi(n) are also discussed.     

(XY)12 (X═B, Al; Y═P)团簇的结构与稳定性

采用B3LYP/6-31G*方法, 对(XY)₁₂ (X═B, Al; Y═P)笼状团簇的同分异构体进行优化, 筛选出能量最低的构型. 讨论它们的几何构型、HOMO-LUMO能隙、生成焓、核独立化学位移(NICS)和自由能. 得到(BP)₁₂和(AlP)₁₂团簇的最稳定构型均为具有T_h对称性的四、六元环组成的笼, 亚稳态结构中含有五元环.     

A further study on closo boron hydrides B_(16)H_(16)~(2-)(D_2) and B_(16)H_(16)(Td) using ab initio molecular orbital theory

Ab initio molecular orbital calculations of doubly negative charged B16H162-(D2) and neutral B16H16(Td) have been done at the HF/6-31G level.They are predicted to be chemically and kinetically stable by vibrational analyses on their respective energy hypersurface of the HF/6-31G level.The geometrical structure of the species B16H1622-(D2) was discussed.     

B24N24团簇的结构与稳定性

采用密度泛函理论,在B3LYP/6-31G^*水平下,对B₂₄N₂₄笼状团簇的12种异构体进行了优化,并对它们的几何构型、化学键性质、振动光谱和稳定性进行了探讨.研究表明:具有S₈对称的含有2个八元环、8个四元环和16个六元环的结构h是B₂₄N₂₄笼状团簇最稳定的异构体,只存在B-N键,而无N-N和B-B键.含有五元环结构的稳定性最低.B-B和N-N键对的数目越多,结构的稳定性越低.12种异构体的稳定性顺序为h＞a＞b＞I＞g＞l＞c＞k＞j＞d＞e＞f.     

ab initio calculation study on vibrational spectra of C_2B_(10)H_(12),NB_(11)H_(12) and C_2B_(10)H_(11)Cl

Geometrical optimization and theoretical calculation of the vibrational frequencies have been performed for C2B10H12, NB11H12 and C2B10Cl by using Gaussian 92 program at 6-31G basis set. The results obtained in this work are in agreement with experimental ones. The optimized geometry and vibrational spectra show that the icosahedral configuration remains unchanged upon converting from B12H122- to the title compounds. The vibrational spectrum of C2B10H11Cl features the absence of C-Cl stretching vibration. But the (C2B10H11)-Cl vibration mode in the low frequency region is as the case for two-atom molecules if the group (C2B10H11) is considered as a pseudoatom     

Low-energy isomer identification, structural evolution, and magnetic properties in manganese-doped gold clusters MnAu(n) (n = 1-16)

The size-dependent electronic, structural, and magnetic properties of Mn-doped gold clusters have been systematically investigated by using relativistic all-electron density functional theory with generalized gradient approximation. A number of new isomers are obtained for neutral MnAu(n) (n = 1-16) clusters to probe the structural evolution. The two-dimensional (2D) to three-dimensional (3D) transition occurs in the size range n = 7-10 with manifest structure competitions. From size n = 13 to n = 16, the MnAu(n) prefers a gold cage structure with Mn atom locating at the center. The relative stabilities of the ground-state MnAu(n) clusters show a pronounced odd-even oscillation with the number of Au atoms. The magnetic moments of MnAu(n) clusters vary from 3 μ(B) to 6 μ(B) with the different cluster size, suggesting that nonmagnetic Au(n) clusters can serve as a flexible host to tailor the dopant's magnetism, which has potential applications in new nanomaterials with tunable magnetic properties.     

Experimental and theoretical characterization of MSi16(-), MGe16(-), MSn16(-), and MPb16(-) (M = Ti, Zr, and Hf): the role of cage aromaticity

Silicon (Si), germanium (Ge), tin (Sn), and lead (Pb) clusters mixed with a group-4 transition metal atom [M = titanium (Ti), zirconium (Zr), and hafnium (Hf)] were generated by a dual-laser vaporization method, and their properties were analyzed by means of time-of-flight mass spectroscopy and anion photoelectron spectroscopy together with theoretical calculations. In the mass spectra, mixed neutral clusters of MSi(16), MGe(16), and MSn(16) were produced specifically, but the yield of MPb(16) was low. The anion photoelectron spectra revealed that MSi(16), MGe(16), and MSn(16) neutrals have large highest occupied molecular orbital-lowest unoccupied molecular orbital gaps of 1.5-1.9 eV compared to those of MPb(16) (0.8-0.9 eV), implying that MSi(16), MGe(16), and MSn(16) are evidently electronically stable clusters. Cage aromaticity appears to be an important determinant of the electronic stability of these clusters: Calculations of nucleus-independent chemical shifts (NICSs) show that Si(16)(4-), Ge(16)(4-), and Sn(16)(4-) have aromatic characters with negative NICS values, while Pb(16)(4-) has an antiaromatic character with a positive NICS value.     

Geometric and electronic structures of (BeO)(N) (N = 2-12, 16, 20, and 24): rings, double rings, and cages

The structure of (BeO)(N) clusters (N = 2-12, 16, 20, and 24) are investigated using the method combining the genetic algorithm with density function theory. Benchmark calculation indicates that THSSh functional is reliable to predict the structures of (BeO)(N) cluster. The global minimum structures of (BeO)(N) clusters are rings up to N = 5, double rings at N = 6 and 7 and cages at N ≥ 8. Besides, almost all of the structures of (BeO)(N) cluster are aromatic according to the NICS criterion. Adaptive natural density partitioning analysis reveals that C(6), (BN)(3), and (BeO)(3) rings (C(24) and (BeO)(12) fullerenes) are similar in bonding patterns. The building-up principle of (BeO)(N) is different from that of covalent (BN) and ionic (LiF and MgO) clusters.     

A novel polyoxovanadium borate incorporating an organic amine ligand: synthesis and structure of [V12B16O50(OH)7(en)]7-

A novel 1D chain organic-inorganic hybrid polyoxovanadium borate Na[V(12)B(16)O(50)(OH)(7)(en)](2)(enH(2))(6)(enH)(2)(OH)(H(2)O)(19) (1, en = ethylenediamine), based on a [V(12)B(16)O(50)(OH)(7)(en)](7-) cluster unit, has been hydrothermally synthesized and characterized. Interestingly, organic amine is incorporating into the V(12)B(16) clusters.     

十二硼十二氢镍乙二胺晶体结构的研究

Ni(en)_3B_(12)H_(12)晶体属于三方晶系,空间群为R_3,晶胞参数为:a=b=12.890(2),c=23.955(20),α=B=90°,Υ=120°,Z=6。在室温下用CAD-4衍射仪收集单晶衍射强度数据(MOK_α);重原子法和差Fourier法解出全部非氢原子坐标,用加氢程序定出全部氢原子的坐标。各原子坐标及热振动参数经全矩阵最小二乘方修正,对于985个独立衍射点[I≥3σ(I)]最后偏离因子R=0.069。结构分析表明,该化合物属于离子型,Ni(en)_-~(2+)离子和B_(12)H_(12)~(-2)离子间相互以正三角双锥方式配位。Ni(en)~(2+)离子具有D_3对称性,Ni-N平均键长为2.138,B_(12)H_(120~(-2)离子呈正二十面体构型,B-B平均键长为1.786。     

Density functional theory study of anionic and neutral per-substituted 12-vertex boron cage systems, B(12)X(12)(n-) (n = 2, 1, 0)

The 12(12) closomers form a rapidly expanding class of compounds where a 12-vertex cage is surrounded by 12 identical substituents. Density functional theory (B3LYP/6-31G(d)) is used to study a number of these closomers in different states of oxidation (dianion, radical anion, and neutral cages). The cage stability increases as the group electronegativity of the substituent increases. Also, the 12(12) closomer becomes easier to oxidize as the Hammett sigma(p) parameter becomes more negative (electron-donating). As the closomer is oxidized, the size of the cage increases and the B-B distances become more asymmetric. The Raman-active breathing mode in the 404-434 cm(-1) range moves to lower frequency as the cage is oxidized, which is caused by removing one or two electrons from a cage-bonding molecular orbital.     

CRYSTAL AND MOLECULAR STRUCTURE OF N_2-[(4-METHYLPHENYL)-SULFONYL]-CLUTAMINE (C_(12)H_(16)N_2O_5S)

<正> C12H16N2O5S, Mr = 300. 34, monbclinic, P21, a = 12. 748(4), b = 5. 240(1), c=21. 356(4)(?); β=93. 28(2)°, V = 1428. 1(7) (?)3. Z = 4, Dc = 1. 397gcm-3, λ=0. 71073(?). Full matrix least-squares refinement, final R = 0. 042, Rw = 0. 045 for 2050 unique reflexions with I≥3σ(I). The two molecules in the asymmetric unit are connected by two hydrogen bonds to form a dimer.     

On the viability of small endohedral hydrocarbon cage complexes: X@C4H4, X@C8H8, X@C8H14, X@C10H16, X@C12H12, AND X@C16H16

Small hydrocarbon complexes (X@cage) incorporating cage-centered endohedral atoms and ions (X = H(+), H, He, Ne, Ar, Li(0,+), Be(0,+,2+), Na(0,+), Mg(0,+,2+)) have been studied at the B3LYP/6-31G(d) hybrid HF/DFT level of theory. No tetrahedrane (C(4)H(4), T(d)()) endohedral complexes are minima, not even with the very small hydrogen atom or beryllium dication. Cubane (C(8)H(8), O(h)()) and bicyclo[2.2.2]octane (C(8)H(14), D(3)(h)()) minima are limited to encapsulating species smaller than Ne and Na(+). Despite its intermediate size, adamantane (C(10)H(16), T(d)()) can enclose a wide variety of endohedral atoms and ions including H, He, Ne, Li(0,+), Be(0,+,2+), Na(0,+), and Mg(2+). In contrast, the truncated tetrahedrane (C(12)H(12), T(d)()) encapsulates fewer species, while the D(4)(d)() symmetric C(16)H(16) hydrocarbon cage (see Table of Contents graphic) encapsulates all but the larger Be, Mg, and Mg(+) species. The host cages have more compact geometries when metal atoms, rather than cations, are inside. This is due to electron donation from the endohedral metals into C-C bonding and C-H antibonding cage molecular orbitals. The relative stabilities of endohedral minima are evaluated by comparing their energies (E(endo)) to the sum of their isolated components (E(inc) = E(endo) - E(cage) - E(x)) and to their exohedral isomer energies (E(isom) = E(endo) - E(exo)). Although exohedral binding is preferred to endohedral encapsulation without exception (i.e., E(isom) is always exothermic), Be(2+)@C(10)H(16) (T(d)(); -235.5 kcal/mol), Li(+)@C(12)H(12) (T(d)(); 50.2 kcal/mol), Be(2+)@C(12)H(12) (T(d)(); -181.2 kcal/mol), Mg(2+)@C(12)H(12) (T(d)(); -45.0 kcal/mol), Li(+)@C(16)H(16) (D(4)(d)(); 13.3 kcal/mol), Be(+)@C(16)H(16) (C(4)(v)(); 31.8 kcal/mol), Be(2+)@C(16)H(16) (D(4)(d)(); -239.2 kcal/mol), and Mg(2+)@C(16)H(16) (D(4)(d)(); -37.7 kcal/mol) are relatively stable as compared to experimentally known He@C(20)H(20) (I(h)()), which has an E(inc) = 37.9 kcal/mol and E(isom) = -35.4 kcal/mol. Overall, endohedral cage complexes with low parent cage strain energies, large cage internal cavity volumes, and a small, highly charged guest species are the most viable synthetic targets.     

(ZnS)6~12团簇三阶非线性光学性质的理论研究

在TDDFT/Lanl2DZ+6-31G*水平下对(ZnS)6~12半导体团簇的三阶非线性光学性质进行了计算, 并用态求和(SOS)方法得到静态三阶宏观极化率χ(3)和0~2.5 eV范围内输入光子能量对三阶微观极化率γ的动态行为. 结果表明, (ZnS)6~12的χ(3)值比其它半导体团簇的略好. 且(ZnS)7和(ZnS)11分别在1.6和2.0 eV处出现了很大的γ值, 为-2.38×10-33和1.26×10-33 esu. 在此输入光子能量处激发, 它们将会产生很强的三阶非线性光学效应.