聚酰胺-胺型树枝状化合物与四氯化钛的配合及其催化作用初步研究

树枝状化合物因具有独特结构,近年来基分子修饰及功能化研究十分活跃,许多研究结果表明,由发散法合成的树枝状分子（如聚酰胺－胺型,简称PAMAM）其低代数（3.0代以下）为敞开和相对疏松的结构,高代数（4.0代以上）则是表面紧密堆积的结构,其性质与胶团相似,它的内部空隙可以包容小分子,因此可用于药物或催化剂的载体,Meijer等已成功的将4－硝基苯甲酸、Bengal Rose等小分子包埋在树枝状分子中,并深入研究了释放小分子的方法,Knapen等也报道了过渡金属与树枝状分子配合物作为催化剂的反应,本文合成了聚酰胺－胺型树枝状化合物（3.0代）;用苯甲醛、苄基氯和三苯甲基氯等对其进行了修饰,使它外层的每个－NH2分别连接1个、2个或3个苯环;用TiCl4与这些经修饰的化合物进行配合,测定了含Ti量,并对它的催化性质做了初步探索。     

Structural and Thermodynamic Properties of Gallium Arsenide with Hexagonal Wurtzite Structure from First-Principles Analysis

A first-principles plane wave method with the ultrasoft pseudopotential scheme in the frame of the generalized gradient approximation （GGA） is performed to calculate the lattice parameters, the bulk modulus Bo and its pressure derivative B~o of the hexagonal wurtzite GaAs （w-GaAs） by the Cambridge serial total energy package （CASTEP）. Our calculations show that the most stable structure of the w-GaAs corresponds to the axial ratio c/α = 1.651 and the internal parameter u = 0.374, consistent with other theoretical results. Also, the thermodynamic properties of the w-GaAs are investigated from the quasi-harmonic Debye model. The dependences of the normalized lattice parameters α/α0, c/c0, the axial ratio c/α, the normalized volume V/V0, the heat capacity Cv and the thermal expansion α on pressure P and temperature T are also obtained successfully.