长链烷基胺氢卤酸盐的热致相变

差示扫描量热法（ＤＳＣ）结果表明，烷基胺氢卤酸盐化合物的相变温度与化合物烷基链链长之间存在明显的规律性，固－固结构相变的主相变峰温随烷基链链长的递增而升高，其逆相变过程表现出明显的热滞后现象；而熔融相变温度则随烷基链链长的递增而降低；实验结果还表明，试样的陈化放置过程以及结晶过程中所用的溶剂对化合物的热致相变历程都有明显的影响。     

不同氧化态的离子掺杂对limn2o4电化学性能的影响

以CH3COOLi·2H2O、(CH3CO2)2Mn·4H2O、氧化物和柠檬酸为原料,采用流变相法经过2次灼烧后得到了不同氧化态离子掺杂的尖晶石化合物LiMn1.95M0.05O4(M:Li,Mg,Co,Ti,V)。通过X射线衍射测试技术对合成的产物物相进行表征,所得产物均具有纯相尖晶石结构。同时应用软件计算了其晶格常数,结果发现金属离子的掺杂不同程度地减少晶格大小。通过循环伏安法研究发现,在4V区域有2步可逆过程发生,对应于锂离子的脱嵌。掺杂的金属离子对于峰电位以及峰面积都有影响。Mn3 的含量越低,峰的面积越小。金属离子与氧的键能越大,峰电位越高。50次充放电循环测试表明,通过掺杂改性来改善尖晶石LiMn2O4的电化学性能时,在掺杂相同量阳离子的尖晶石化合物中,以选择氧化态为Co3 掺杂的化合物具有最佳的充放电容量和循环性能。     

Quantum chemical study on the abstraction reaction of alkylidenegermylene with oxirane and thiirane

The mechanisms of theion reaction of alkylidenegermylene with oxirane and thiirane have been characterized detail in using density functional theory, as well as ab initio method, including geometry optimization and vibrational analysis for the involved stationary points on the potential energy surface. Energies were calculated by CCSD(T)/6-311G(d)//B3LYP/6-311G(d,p) method for the involved conformations. The results show that the reaction pathways for both reactions consist of two ways: (1) the reactants can yield bent products (P1; P4) by syn-isomers; (2) the reactants can also yield three-membered products (P2; P5) by anti-isomers, which then further react with oxirane and thiirane to form the ultimate products (P3-1, P3-2; P6). Furthermore, a comparison with alkylidenecarbene, oxirane, and thiirane was done.     

Cation identity dependence of crown ether photonic crystal Pb<Superscript>2+</Superscript> sensing

We quantitatively modeled the volume phase transition of a hydrogel containing a crystalline colloidal array with a crown ether ligand which binds Pb²⁺. The hydrogel volume response and the wavelength diffracted depend on the Pb²⁺ concentration and on both the ionic strength and the valence of the nonbinding ionic species. We successfully modeled the response of this hydrogel Pb²⁺ sensor to ionic strength and the cation valence of the added salts. Figure Cation identity dependence of crown ether photonic crystal Pb⁺ sensing     

Phase diagrams of the KF-K<Subscript>2</Subscript>TaF<Subscript>7</Subscript> and KF-Ta<Subscript>2</Subscript>O<Subscript>5</Subscript> systems

The phase diagrams of the systems KF-K₂TaF₇ and KF-Ta₂O₅ were determined using the thermal analysis method. The phase diagrams were described by suitable thermodynamic model. In the system KF-K₂TaF₇ eutectic points at x _KF=0.716 and t=725.4°C and at x _KF=0.214 and t=712.2°C has been calculated. It was suggested that K₂TaF₇ melts incongruently at around 743°C forming two immiscible liquids. The system KF-Ta₂O₅ have been measured up to 8 mol% of Ta₂O₅. The eutectic point was estimated to be at x _KF∼0.9 and t∼816°C. The formation of KTaO₃ and K₃TaO₂F₄ compounds has been observed in the solidified samples.     

Synthesis and Crystal Structure of 4,4＂-Diamino-N,N＇-diethyl Bisbenzenesulfamide

A new compound of 4,4'-diamino-N,N'-diethyl bisbenzenesulfamide (C18H26N4O4S2,Fw = 426.55) has been synthesized and its structure was determined by X-ray crystallography method. The crystal belongs to the monoclinic system, space group P21/c with a = 10.0623(9), b =13.6759(13), c =15.5309(14) (A),β = 100.482(2)°, V= 2101.6(3)(A)3, Dc = 1.348 g/cm3, F(000) = 904,μ = 0.285 mm-1, Z = 4, the final R = 0.0512 and wR = 0.1363 for 3485 observed reflections with I ＞2σ(Ⅰ). The structure of the title compound is pseudo secondary axisymmetric, and the two sulfamide-groups show distorted tetrahedral configurations.     

甲硫醇和氢原子反应的从头算直接动力学

利用双水平直接动力学方法对反应CH3SH+H的微观机理和动力学性质进行了理论研究.对于此反应的三个反应通道,即—SH和—CH3基团上的两个氢提取通道及一个取代通道,在MP2/6-311+G(d,p)水平上优化得到了各稳定点的结构及振动频率,并在G3(MP2)水平上进行了单点能量计算以获得更精确的能量信息;在此基础上运用结合小曲率隧道效应校正的变分过渡态理论(CVT/SCT)计算了各反应通道在220-1000 K温度区间的速率常数.计算结果表明提取—SH基团上H的反应通道R1在整个反应温度区间都是主要通道,而随着温度的升高,低温下的次要反应通道——取代通道R3变得越来越重要,并且在高温下将成为一个竞争的反应通道;提取—CH3基团上H的反应通道(R2)由于具有较高的反应能垒,因而,其对总反应速率常数的贡献可以忽略.计算得到的总反应速率常数与已有的实验值符合得很好,进而我们预测了该反应在220-1000 K温度范围内速率常数的表达式为:k=5.00×10-18T2.39exp(-119.81/T),为将来的实验研究提供参考.     

Crystal structures and chemistry of double perovskites Ba2M(II)M′(VI)O6 (M=Ca, Sr, M′=Te, W, U)

Structures of the double perovskites Ba₂M(II)M ′(VI)O₆ (M=Ca, Sr, M′=Te, W, U) at room temperature have been investigated by the Rietveld method using X-ray and neutron powder diffraction data. For double perovskites with M=Sr, the observed space groups are I2/m (M′ =W) and (M′=Te), respectively. In the case of M=Ca, the space groups are either monoclinic P2₁/n (M′=U) or cubic (M′=W and Te). The tetragonal and orthorhombic symmetry reported earlier for Ba₂SrTeO₆ and Ba₂CaUO₆, respectively, were not observed. In addition, non-ambient X-ray diffraction data were collected and analyzed for Ba₂SrWO₆ and Ba₂CaWO₆ in the temperature range between 80 and 723 K. It was found that the rhombohedral structure exists in Ba₂SrWO₆ above room temperature between the monoclinic and the cubic structure, whereas the cubic Ba₂CaWO₆ undergoes a structural phase transition at low temperature to the tetragonal I4/m structure.     

Further aspects of the roaming mechanism in formaldehyde dissociation

Recently we reported a novel “roaming” dissociation pathway of formaldehyde in which one of the H atoms strays far from the minimum energy reaction path, explores a broad region of the potential energy surface, then abstracts the remaining H atom to form molecular products, without going near the configuration of the conventional transition state saddle point. The detailed dynamics of the abstraction mechanism and its energy dependence have already been reported. Here, with a combination of experimental and theoretical results, we examine the roaming behavior at the energetic extremes. We show evidence of roaming below the threshold of the radical dissociation channel and consider the implications of this and the possible existence of a transition state for the roaming mechanism. We also show the occurrence of roaming up to 3200 cm⁻¹ above the threshold of the triplet dissociation channel. In addition, we present results affording deeper insight into the dynamics of the roaming mechanism: we show evidence of roaming leading to CO in v = 1, and examine the issue of nuclear spin conservation during dissociation via the roaming mechanism.     

Exploration for electronic transitions and photodissociation mechanism of hydrogen iodide

The electronic transitions and excited-state fragmentation of hydrogen iodide have been studied within the A-band continuum. The extinction intensity for the excitations from the ground to the low-lying electronic states are derived by performing the wave packet simulations of nuclear dynamics in this study. The quantum yields of the spin-excited I* product at the different photon energies are determined as well. The results suggest that the possibility of intersystem crossing can be neglected. Employing the time-dependent density functional theory (TDDFT), the four highest occupied and the two lowest unoccupied orbitals of hydrogen iodide have been analyzed, and the transition to the state is found to be most probable in the first absorption band.