Theoretical Investigations on the Structural and Electronic Properties of WO_3 Polymorphs

The structural characteristic and electronic properties of seven WO_3 bulk polymorphs have been studied by first-principles density functional theory(DFT) calculations. Our calculation results indicate that according to the energy of WO_3 per unit, the stability of different WO_3 systems reduces in turn in the following order: monoclinic WO_3, orthorhombic WO_3, tetragonal WO_3, triclinic WO_3, hexagonal WO_3 and cubic WO_3. And when the unit cell is distorted from the cubic framework, the alternatively long and short W–O bonds are formed, implying an improvement of bonding-antibonding splitting associated with the interactions between W and O atoms. The deformation of the WO6 octahedron enhances the stability of the system to some extent though the energy difference between various WO_3 phases is small( 0.1 eV/per WO_3 unit). Besides, the band gap tends to enlarge accompanied with the symmetry decrease of WO_3 bulk. According to the band structures, the minimum band gaps for those WO_3 polymorphs are direct at the Γ point except for the simple cubic and hexagonal structures. In addition, for all the WO_3 phases, the compositions of the valance band maximum(VBM) and conduction band minimum(CBM) are the same, which are relative to the O 2 p and W 5 d orbitals, respectively.     

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同程度的决定因素.     

七氟异丁腈负离子结构与反应活性的理论研究

新型环保绝缘气体七氟异丁腈(C4)在高压输电应用中备受关注. 本文采用多种高精度量子化学理论方法研究了C4吸附电子后形成C4^-负离子的结构、 光谱、 寿命以及与CO₂的反应机理和动力学. 结果表明, 电子进入C≡N的π^*反键轨道, 通过弯曲C—C=N形成C4^-负离子, 绝热电子亲合能的最佳预测值为0.30 eV. 在 0~2 eV范围内C4^-具有显著的光电子吸收峰, 亚稳态C4^-负离子经约9 kJ/mol能垒断裂C—F键生成稳定的长寿命[F...(CF₃)₂CCN]^-中间体. C4^-+CO₂反应存在进攻F或CN上的C和N 3种复合-解离机理, 在电气应用条件下, 以CO₂进攻氰基CN途径为主, 诱发负电荷从CN向CO₂转移.     

实验和理论研究石墨烯氧化物的铁电性

基于独特的结构和性质, 石墨烯在很多领域都表现出了巨大的潜力. 作为制备石墨烯的主要母体材料, 石墨烯氧化物在室温条件下被观测到具有弱的铁电性. 石墨烯氧化物的表面和边界上会存在大量的羟基, 这些羟基有序重复排列而构成了一维的氢键链, 这些有序氢键链可能是石墨烯氧化物呈现铁电性能的主要原因.     

The Molecular and Electronic Structure of [ReOX3(AsPh3)(OAsPh3)] Complexes (X = Cl,Br)

New rhenium oxo-complexes [ReOX₃(OAsPh₃)(AsPh₃)] (X = Cl and Br) have been synthesised and characterised by X-ray diffraction, IR, electronic and magnetochemical measurements. They were obtained in high yield in reactions between [ReOX₃(AsPh₃)₂] and acetonitrile in air.     

MgO缺陷和不规则表面吸附Cl2的电子结构研究

采用从头算程序对MgO表面 3种不同配位位置吸附Cl2 的构型进行优化 ,并用扩展休克尔紧束缚 (EHT)晶体轨道方法对MgO的缺陷和不规则表面吸附Cl2的可能构型进行能带计算 ,讨论了吸附前后能带组成和成键性质的变化。研究表明 :MgO表面吸附Cl2 将更趋向于吸附在O原子上而非Mg原子上 ,而且在 3种配位中MgO表面三配位氧最有利于吸附Cl2 ;吸附时 ,电子从O原子转移到Cl2 分子的反键轨道 ,但是各种吸附构型的MgO表面对Cl2 的吸附作用均比较微弱 ,是典型的物理吸附。     

V（acac）3—AI（i—BU）2CI催化体系相态的研究

研究了V(acac)3-AI(i-BU)2CI催化体系的相态。通过Tyndall效应、电镜观察和超过渡实验,证明了在溶有丁二烯的甲苯溶剂中V(acac)3-AI(i-BU)2CI催化体系以小颗粒分散,粒径在1－100nm之间,为胶体催化剂,属于高度分散的多相催化体系。催化剂颗粒是无定形的,其活性中心位于胶粒表面,以较佳配比所得到的催化剂颗粒较小、分布均匀,对丁二烯聚合反应具有较高的催化活性。     

Crystal Structure,Magnetic Properties,and Electronic Structure of Ni(NCNH2)4Cl2 and Co(NCNH2)4Cl2

The crystal structures of Ni(NCNH₂)₄Cl₂ and Co(NCNH₂)₄Cl₂, the first complexes with cyanamide as a neutral ligand, have been determined from single crystal data (Im3m, Z = 6, a = 1259.3(2) pm, R₁ = 0.0245 for Ni(NCNH₂)₄Cl₂ and a = 1266.3(2) pm, R₁ = 0.0241 for Co(NCNH₂)₄Cl₂; both 329 intensities and 23 parameters). Ni²⁺ and Co²⁺ are octahedrally coordinated by four equatorial H₂NCN molecules and two axial chloride ions, and the 20 and 19 electron octahedral complexes are connected by a network of hydrogen bonds. The cyanamide ligands are slightly bent (166°), and the two N–C distances are 112 and 133 pm. Ni(NCNH₂)₄Cl₂/Co(NCNH₂)₄Cl₂ are Curie paramagnets with two/three unpaired electrons.     

Geometry and Electronic Structure of CuCl(6)(4-) Polyhedra Doped into (3-Chloroanilinium)(8)[CdCl(6)]Cl(4)-An EPR and Structural Investigation

The EPR single-crystal and powder spectra of mixed crystals of (3-chloroanilinium)(8)(Cd(1-x)Cu(x)Cl(6))Cl(4) are measured as a function of temperature and x and analyzed with respect to the geometry and bonding properties of the CuCl(6) polyhedra. These undergo strong distortions due to vibronic Jahn-Teller coupling, with the resulting tetragonal elongation being superimposed by a considerable orthorhombic symmetry component induced by a host site strain acting as a compression along the crystallographic a axis. This strain becomes apparent in the cadmium compound (x = 0), whose crystal structure is also reported [a = 8.701(2) ?, b = 13.975(2) ?, c = 14.173(2) ?, alpha = 81.62(1) degrees, beta = 72.92(1) degrees, gamma = 77.57(1) degrees, triclinic P&onemacr;, Z = 1]. A calculation of the ground state potential surface and its vibronic structure nicely reproduces the g values, Cu-Cl spacings, and ligand field data. At high copper concentrations (including x = 1), the CuCl(6) polyhedra are coupled elastically, with the long axes of neighboring polyhedra having perpendicular orientations. The elastic correlation presumably is not of the long-range antiferrodistortive type, however. Above about 55 K, the angular Jahn-Teller distortion component becomes dynamically averaged within the time scale of the EPR experiment, leading to local tetragonally compressed CuCl(6) octahedra.     

TiO2(110)表面负载W3O10团簇构型和电子结构的理论研究

采用基于第一性原理的分子动力学和量子力学相结合的方法, 对非化学计量比富氧型钨氧化物团簇W₃O₁₀在TiO₂(110)表面负载的构型和电子结构进行了系统研究. 研究结果表明, 热力学最稳定的负载构型为W₃O₁₀团簇通过端氧原子和W原子形成四根Ti-O键和两根W-O键吸附在TiO₂(110)表面. 负载W₃O₁₀团簇后, 有较多电子从TiO₂表面转移到团簇上, TiO₂表面不再保持半导体性质, 相应地, 表面功函上升. 比较负载前后团簇的稳定性可知, 可以通过沉积在合适的固体表面来稳定气相中的不稳定构型.     

Theoretical study on the isomeric structures and the stability of silylenoid (Tsi)Cl2SiLi (Tsi = C(SiMe3)3)

The structures and isomerization of silylenoid (Tsi)Cl(2)SiLi (Tsi = C(SiMe(3))(3)) were studied by density functional theory (DFT) at the B3LYP/6-31G(d) level. Four equilibrium structures and three isomeric transition states were located. The three-membered ring and p-complex structures, 1 and 2, are the two most stable forms. Two other local minima, the sigma-complex 3 and tetrahedron structure 4, should rearrange to 1 with very low barriers, and then to the most stable isomer 2. To exploit further the stability of silylenoid (Tsi)Cl(2)SiLi, the insertion reactions of 2 and silylene (Tsi)ClSi into the HF molecule have been investigated at the B3LYP/6-31G(d) level, respectively. The results show that the insertion of 2 into HF is very similar to that of (Tsi)ClSi into HF, but the latter is more favorable. To probe the influence of the substituent Tsi on the stability of silylenoid (Tsi)Cl(2)SiLi, the isomers and insertion reaction of silylenoid CH(3)Cl(2)SiLi were investigated in a similar way of those with (Tsi)Cl(2)SiLi. The results indicate that silylenoid containing very bulky group Tsi exhibits unusual stability because of the severe steric hindrance produced by Tsi at the center to which it is attached.     

Electronic emission and absorption spectroscopy of the rhenium complexes Re(CO)3Cl(phosphine)2

Summary The compounds Re(CO)₃Cl(L)₂,L=triphenylphosphine, tri-p-tolyphosphine, and Re(CO)₃-Cl(L),L=1,2-bis(diethylphosphinoethane) are luminescent in solution and in crystalline form when excited between 351 nm and 514 nm at temperatures ranging from 10 K to room temperature. The absorption spectra contain a weak (E 10M ^–1 cm^–1) band in the visible region of the spectrum between 400 and 500 nm. The lowest energy transition giving rise to these spectroscopic features is assigned to a d-d transition.

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Elektronenemissions- und Absorptionsspektroskopie der Rheniumkomplexe Re(CO)₃Cl(Phoshin)₂

Zusammenfassung Die Verbindungen Re(CO)₃Cl(L)₂ mitL=Triphenylphosphin, Tri-p-tolylphosphin und Re(CO)₃Cl(L)₂ mitL=1,2-Bis(diethylphosphinoethan) sind in Lösung und im kristallinen Zustand bei Anregung zwischen 351 und 514 nm im Temperaturbereich von 10 K bis Raumtemperatur lumineszent. Die Absorptionsspektren enthalten im sichtbaren Bereich zwischen 400 und 500 nm eine schwache Bande von 10M ^–1 cm^–1. Der energetisch tiefstliegende Übergang, der für dieses Verhalten verantwortlich ist, wird einem d-d-Übergang zugeordnet.

     

B8N12簇的结构和振动光谱的理论研究

用量子化学从头计算方法研究Ｂ_８Ｎ_（１２）的几何构型、电子结构和振动光谱，讨论其稳定性和化学反应性质。     

类水滑石材料主客体插层结构的构筑及特性的理论研究

因主体层板和层间客体具有丰富的可调性,类水滑石材料(LDHs)在催化、吸附、生物医药及光、电、磁等方面展现出了广阔的应用前景.近年来理论研究已成为揭示LDHs微观结构和性质的重要手段,本文系统综述了LDHs材料主体结构、客体结构以及主客体相互作用3个方面的理论研究工作进展,及其在作为光驱动催化剂方面应用的理论研究.从主体元素构成、元素比例、电荷分布、拓扑结构转变、能带结构、态密度、层间阴离子组成、离子交换性能、主客体作用力、能量性质及光催化性能等方面,在原子、电子尺度上揭示了LDHs材料结构-性能之间的构效关系,为以其为材料平台构筑一系列基于超分子插层结构主客体间相互作用的新型功能材料、扩展材料的功能性提供了丰富的理论信息和有益指导.     

Theoretical Investigation on the Geometries and Properties of Guanine-BX3 （X = F, Cl） Complex

Geometries and binding energies were predicted at the B3LYP/6-311+G* level for the guanine-BX3 (X = F, Cl) systems and four isomers with no imaginary frequencies have been obtained for both guanine-BF3 and guanine-BCl3, respectively. Single energy calculations using much larger basis sets (6-311+G(2df,p) and aug-cc-pVDZ were carried out as well. It was found that the most stable isomer of guanine-BF3 is BF3 connected to N3 of guanine with the stabilization energy of –19.93 kcal/mol (BSSE corrected), while that of guanine-BCl3 is BCl3 connected to O10 of guanine having stabilization energy of –15.02 kcal/mol at the same level. The analyses for the combining interaction between BX3 and guanine with the atom-in-molecules theory (AIM) and natural bond orbital (NBO) methods have been performed. The results indicated that all the isomers are formed with σ-p type interactions between guanine and BX3, in which pyridine-type nitrogen or carbonyl oxygen or nitrogen atom of amino group offers its lone pair electrons to the empty p orbital of boron atom and the concomitance of charge transfer from guanine to BX3 has occurred. Still, one or two hydrogen bonds exist in some isomers of guanine-BX3 system and contribute to the stability of complex systems. Frequency analysis suggested that the stretching vibration of BX3 undergoes a red shift in complexes. Guanine-BF3 complex is more stable than guanine-BCl3 although the B–Y (Y=N, O) bond distance in the latter is shorter.     

Crystal Structure of Ni(NH3)Cl2 and Ni(NH3)Br2

Ni(NH₃)Cl₂ and Ni(NH₃)Br₂ were prepared by the reaction of Ni(NH₃)₂X₂ with NiX₂ at 350 °C in a steel autoclave. The crystal structures were determined by X‐ray powder diffraction using synchrotron radiation and refined by Rietveld methods. Ni(NH₃)Cl₂ and Ni(NH₃)Br₂ are isotypic and crystallize in the space group I2/m with Z = 8 and for Ni(NH₃)Cl₂: a = 14.8976(3) Å, b = 3.56251(6) Å, c = 13.9229(3) Å, β = 106.301(1)°; Ni(NH₃)Br₂: a = 15.5764(1) Å, b = 3.74346(3) Å, c = 14.4224(1) Å, β = 105.894(1)°. The crystal structures are built up by two crystallographically distinct but chemically mostly equivalent polymeric octahedra double chains [NiX_3/3X_2/2(NH₃)] (X = Cl, Br) running along the short b‐axis. The octahedra NiX₅NH₃ share common edges therein. The crystal structures of the ammines Ni(NH₃)_mX₂ with m = 1, 2, 6 can be derived from that of the halides NiX₂ (X = Cl, Br) by successive fragmentation of its CdCl₂ like layers by NH₃.     

C62O3的结构和光谱的理论研究

用ＩＮＤＯ法研究了Ｃ６２Ｏ３的结构与光谱，结果表明，Ｃ６２Ｏ３有Ｃ２０和Ｃ５两种种稳定构型，其中Ｃ２０构型能量较低。利用Ｃ６０的碎片拓扑图讨论基加成及环加成产物对称性的规律，理论计算与＾１３ＣＮＭＲ谱的实验结果相符合。