CnAl (n=2-11)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6-311++G**水平上对CnAl(n=2-11)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, n=2的CnAl团簇基态结构为Al原子与两个C原子相连形成的环状结构, n=3-11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CnAl团簇比n为奇数团族稳定的结论.     

C_nAl~+小团簇结构的几何特征与稳定性

采用密度泛函理论(DFT)的B3LYP方法,研究了CnAl+(n=2-12)团簇的几何结构与电子性质.在6-311++G**水平上对CnAl+(n=2-12)团簇进行了几何构型优化和振动频率计算.结果表明,CnAl+团簇的基态结构为Al原子与Cn链端基配位形成的直线或折线形结构,以及Al原子与Cn环上1个C原子端位相连或打开Cn环与2个C原子相连形成的环状结构.分子总的平均键长随着n的增大逐渐趋于定值(0.138nm).通过对基态结构的能量分析,得到了CnAl+团簇的稳定性信息.     

C_nAl_m~+(n=1～12,m=1,2)团簇几何结构特征与稳定性的量子化学研究

采用密度泛函理论(DFT)的B3LYP方法,在6-311++G**水平上对CnAlm+(n=1～12,m=1,2)团簇的几何和电子结构进行了理论计算,讨论了混合团簇的结构与成键特征,以及振动频率与电荷转移.结果表明,CnAl+团簇的基态结构分别为Al原子与Cn链端基配位形成的直线或折线状结构,以及Al原子与Cn环上1个C原子端位相连或打开Cn环与2个C原子相连形成的环状结构;分子总的平均键长随着n的增大逐渐趋于定值0.138nm.CnAl+2团簇基态结构可以看作是两个较小的Cn/2Al+分子碎片通过端位C原子相互结合形成CcoreAlshell的直线或顺式与反式折线状结构;分子总的平均键长随着n的增大逐渐趋于定值0.141nm.通过对基态结构的能量分析,得到了CnAl+和CnAl+2团簇的稳定性信息.     

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.     

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.     

Quantum Chemical Study of CnAl2^± （n=1～10） Clusters： Structure and Stability

Geometries, electronic structures and vibrational frequencies of CnAl2± clusters have been investigated by using the B3LYP-DFT method in the range of n = 1～10. At the B3LYP/6-311G level, the ground state structures of CnAl2± clusters are planar or linear with terminal aluminum atom. In these structures, the C–C bonds are alternately changed between double and triple. The changing magnitude of the averaged bond length decreases with the increase of cluster size. The energetic analysis showed that CnAl2± clusters with even n are more stable than those with odd n.     

高硅分子筛ZSM-22的动态合成及表征

 以1，6－己二胺（DAH）为模板剂，采用水热条件下的动态合成方法，合成出结晶度良好的ZSM－22晶体．研究表明，合成的关键是避免ZSM－5分子筛的生长，当n（Si）／n（Al）＝25～65，n（H2O）／n（SiO2）＝16．3～40．3，n（DAH）／n（Si）＝0．1～0．6和T＝428～448K时，都能稳定合成出ZSM－22分子筛．采用TEM，XRD，TG－DTA和NH3－TPD等方法，对ZSM－22晶体的形貌，生长动力学，模板剂的作用以及硅铝比对分子筛酸性的影响等进行了较详细的研究．实验结果和理论计算证实，1，6－己二胺分子以首尾相连的方式，线性排列并完全充满ZSM－22的十元环孔道，同时起到结构导向和骨架电荷平衡的作用．     

Cu－Al－MCM－41的Si／Al比对贫燃条件下NO选择性催化还原的影响

 采用连续流动固定床石英反应器，在反应气体为0．1％NO，0．1％C3H6，2％O2，流量为500ml／min以及催化剂装量为0．1g的条件下，考察了Cu－Al－MCM－41的Si／Al比值对贫燃条件下NO选择性还原活性的影响．结果表明，当Cu交换度低于100％时，随Si／Al比值的增加，NO的最大转化率增加．TPD和TPR的研究结果表明，不同的Si／Al比值，改变了Cu在分子筛结构中的化学微环境，使活性中心Cu2＋的浓度和性质发生变化，从而影响其对NO的转化效率．     

直线型CnP^—（n=1～11）结构的理论研究

以激光溅射方法产生了一系列含一个磷原子的碳原子簇负离子．针对其在实验中呈现的奇偶变化规律进行了量子化学从头算研究．在HF／6－311G*水平上（对单重态为RHF，多重态为ROHF）优化了直线型CnP-（n=1～11）键长和能量，计算了相邻簇离子的能量差与成簇碳原子的平均结合能及从CnP-分别解离C、C2、C3、P、CP、C2P等6种通道所需的能量．计算发现，n为奇数的CnP-单重态（1Σ）最稳定，而，n为偶数的簇离子则以三重态（3Σ）的能量较低．所计算的CnP-各结构参数均表现出奇偶交替的变化规律，n为奇数的CnP-相对稳定．     

β沸石催化邻苯二酚-叔丁醇烷基化反应

 考察了Hβ沸石及改性Hβ／Al2O3对邻苯二酚－叔丁醇烷基化反\r\n应的催化性能，并采用XRD和NH3－TPD方法表征了Hβ沸石及改性Hβ／\r\nAl2O3的酸性和结构特性，讨论了其酸性对催化活性及选择性的影响．\r\n结果表明，Hβ沸石和Co改性的Hβ／Al2O3的催化性能都优于目前文献\r\n报道的最好水平，对催化邻苯二酚－叔丁醇烷基化反应具有良好应用开\r\n发前景．     

CnB-的激光等离子体产生与质谱分析

Time-of-flight mass spectrum of C_nB~- has been recorded on a selfbuilt instrument with laser vaporization of tetraphenylboron sodium. By analysis of the com-position of the anions, it is found that number of the boron atoms in any of these ions equals to the number of the charges carried by the anion, and the sum of the numbers of the carbon and boron atoms in these species are always the odd numbers. The experimental results show that boron atom has a strong tendency to attract an electron so that those C_nB~- will have similar electronic structures as C_n, and carbon clusters with odd members are always more stable than their even neighbors.     

Stabilization energies of extensively conjugated propargylic radicals

G3(MP2) and other model chemistry calculations indicate that stabilization energies of extensively conjugated allylic radicals H2(C=C)nCH2*, n = 1-4, increase monotonically as the number of repeating C=C units increase. In contrast, stabilization energies of the analogous propargylic radicals, H(C[triple bond]C)nCH2*, decrease beyond n = 2. Breaking up the number of contiguous conjugated C[triple bond]C units in conjugation with the odd electron enhances rather than diminishes stability. These results complement previous findings of significant differences in the stabilization of conjugated ground-state polyenes vs polyynes.     

Linear carbon chains of type SiCnO (n = 3-8): results of coupled cluster calculations

On the basis of (R)CCSD(T) calculations with the cc-pVQZ basis set, accurate equilibrium bond lengths (ca. 0.0005 A accuracy) are established for linear carbon chains of type SiCnO with n = 3-8. SiC and CO equilibrium bond lengths are in the range 1.683-1.735 and 1.165-1.167 A, respectively. A narrow range (1.272-1.287 A) is obtained for all 25 carbon-carbon equilibrium distances. The equilibrium dipole moments (mu(e)) exhibit large correlation effects. The mu(e) values for the closed-shell species with even integer n are larger than those for the triplet ground states of SiCnO chains with odd n values. Various spectroscopic constants such as harmonic vibrational wavenumbers, vibration-rotation coupling, and l-type doubling constants are calculated. The ground-state rotational constants of SiC3O, SiC4O, and SiC5O are predicted with ca. 0.1% accuracy to be 1386.5, 867.0, and 564.4 MHz.     

Si_2C_(m-2)(m=4～15)团簇的结构与稳定性

用密度泛函理论(DFT)的B3LYP/6-31G*方法, 对Si2Cm-2(m = 4~15)团簇的几何构型、电子结构、振动频率等性质进行了研究, 讨论了化学键的特征和热力学稳定性, 比较了Si2Cm-2团中环状和线状结构的差异。结果表明, m = 4~13的团簇为线状结构, m=14~15的团簇为环状结构。在线状结构中, 随着m增大, 自旋多重度出现1、3交替变化, 并且Si原子倾向于在C链端部成键;环状结构中, C原子形成环状, 2个Si原子处于椭圆环状构型的两端。m 为奇数的Si2Cm-2团簇比m为偶数的更为稳定。     

Parity Alternation of Silicon-doped Ternary Cationic Clusters HC_nSi_2~+(n=1～9)

Systematic study on the electronic/geometrical structures and the parity alternation effect of silicon-doped ternary cationic clusters HCnSi2＋（n = 1 ~9） have been carried out at the coupled cluster level. The ground-state （G-S） isomers of the clusters have been defined. The C, chains of the G-S isomers display polyacetylene-like structures. The even-n cations are more stable than the odd-n ones. Such a trend of even/odd alternation has been elaborated based on concepts of the bond character, atomic charge, incremental binding energy, ionization potential, proton affinity and fragmentation energies of the systems. The findings accord with the relative intensities of HC,,Si2＋ species recorded in the related mass spectrometric experiments.     

Closed-shell polycyclic aromatic hydrocarbon cations: a new category of interstellar polycyclic aromatic hydrocarbons

Density functional theory has been employed to calculate the harmonic frequencies and intensities of a range of polycyclic aromatic hydrocarbon (PAH) cations that explore both size and electronic structure effects on the infrared spectroscopic properties of these species. The sample extends the size range of PAH species considered to more than 50 carbon atoms and includes several representatives from each of two heretofore unexplored categories of PAH cations: (1) fully benzenoid PAH cations whose carbon skeleton is composed of an odd number of carbon atoms (C(odd) PAHs); and (2) protonated PAH cations (HPAH+). Unlike the radical electronic structures of the PAH cations that have been the subject of previous theoretical and experimental work, the species in these two classes have a 'closed'-shell electronic configuration. The calculated spectra of circumcoronene, C54H18, in both neutral and (radical) cationic form are also reported and compared with those of the other species. Overall, the C(odd) PAHs spectra are dominated by strong CC stretching modes near 1600 cm(-1) and display spectra that are remarkably insensitive to molecular size. The HPAH+ species evince a more complex spectrum consistent with the added contributions of aliphatic modes and their generally lower symmetry. Finally, for both classes of closed-shell cations, the intensity of the aromatic CH stretching modes is found to increase with molecular size far out of proportion with the number of CH groups, approaching a value more typical of neutral PAHs for the largest species studied.     

Rotational spectra of the carbon-chain radicals HC5O, HC6O, and HC7O

Three new free carbon-chain radicals, HC5O, HC6O, and HC7O, and their deuterated isotopic species have been observed by Fourier transform microwave spectroscopy of a supersonic molecular beam. In contrast to the shorter HCnO radicals, these all have linear heavy-atom backbones and 2Pi electronic ground states. Like the isovalent HCnS radicals, the ground states of the HCnO radicals alternate with odd and even numbers of carbon atoms: those of HC5O and HC7O are 2Pi1/2 and that of HC6O is 2Pi3/2. From frequency measurements between 6 and 26 GHz, the rotational constant B, the centrifugal distortion constant D, and the lambda-type doubling and magnetic hyperfine constants have been determined to high precision for each chain. Predicted properties from coupled-cluster calculations are also reported for chains up to HC9O. The production of HCnO radicals for n even was highly favored when O2 was used as the source of oxygen, but those with n odd were best produced with CO.     

(Cl2AlNH2)n和(H2AlNH2)n(n=1～5)簇结构及其热力学性质

用HF自洽场理论和密度泛函理论(DFT)的B3LYP方法,在6 31G水平上研究了低聚物(Cl2AlNH2)n和(H2AlNH2)n(n=1～5)簇的几何构型、电子结构和聚合反应热力学性质,比较了两个系列化合物中化学键的强度.结果表明,Cl2AlNH2和H2AlNH2分子为C2 (EC)平面型结构,其中Al－N为由一个σ键和一个键组成的双键.(Cl2AlNH2)n和(H2AlNH2)n(n=1～5)分子为Dnh对称,Al－N是典型的σ单键 .低聚物(Cl2AlNH2)n和(H2AlNH2)n的稳定性顺序分别为: 3 > 2 > 4> 5 > 1和8 > 7 > 9 > 11 > 6.