NH3与BeH2反应机理的密度泛函理论研究

金属-N-H体系储氢材料在放氢反应过程中往往伴随着NH_3的释放,且NH_3会对材料的储放氢性能产生重要影响.采用密度泛函理论当中的杂化密度泛函(B3LYP)方法,6-311G(d,p)基组水平上对NH_3与BeH_2的微观反应机理进行了理论计算分析,对得到的中间体和过渡态进行频率计算和内禀反应坐标(IRC)分析,以判断中间体和过渡态的正确性和相互连接关系.使用QCISD方法在6-311G(d,p)基组水平对各驻点的单点能进行计算,给出能量信息.计算结果表明:BeH_2与NH_3主要以摩尔比为1:2进行反应,分两步氢取代过程,生成产物Be(NH_2)_2和2H_2.反应所释放的H_2中两个H原子分别来源于BeH_2和NH_3,反应的关键是脱氢,主要在于克服N—H键断裂所需能量.相比较而言从NH_3中脱氢比从—NH_2中脱氢较易.     

新疆高师院校中学化学实验课程内容建构与实验模式研究

通过对新疆高师院校中学化学实验内容需求现状进行调查分析,并依据分析结果,构建出适合新疆高师院校的中学化学实验课程体系,提出了适应新疆高师院校的中学化学实验模式,以满足新疆高师院校化学专业师范生成长的实际需要.     

A semi-numerical method for periodic orbits in a bisymmetrical potential

We use a semi-numerical method to find the position and period of periodic orbits in a bisymmetrical potential, made up of a two dimensional harmonic oscillator, with an additional term of a Plummer potential, in a number of resonant cases. The results are compared with the outcomes obtained by the numerical integration of the equations of motion and the agreement is good. This indicates that the semi-numerical method gives general and reliable results. Comparison with other methods of locating periodic orbits is also made.     

芳基吡唑腙及其双杂环化合物的合成与抗菌活性

通过1-苯基-3-(4-甲基苯基)-4-甲酰基吡唑与芳氧乙酰肼的加成反应,合成了5个新型的吡唑腙类化合物(3a～3e);3在酸性条件下环合,合成了5个新型的吡唑双杂环化合物(4a～4e). 3和4的结构经1H NMR,IR,MS和元素分析表征.对3和4分别进行了棉花枯萎病菌(A),棉花黄萎病菌(B),棉花立枯病菌(C),瓜果腐霉病菌(D),番茄早疫病菌(E)及向日葵菌核病菌(F)等初步的抑菌活性测试.结果表明,4的抑菌效果明显高于3;其中4d和4e对A,C和D的抑制率大于90%,对E和F的抑制率大于80%.     

2-芳基-5-(6-哒嗪酮-3-基)-1,3,4-噁二唑的合成

1,4,5,6-四氢-6-哒嗪酮-3-甲酰肼(1)和1,6-二氢-6-哒嗪酮-3-甲酰肼(2)与芳香醛反应得到相应的芳香醛腙3a～3g和5a～5g, 再将3a～3g, 5a～5g在溴的作用下, 合环得到一系列1,3,4-噁二唑的衍生物4a～4g和6a～6g. 化合物的结构经1H NMR, IR, MS和元素分析得以证实.     

C-Mg掺杂GaN电子结构和光学性质的第一性原理研究

基于密度泛函理论第一性原理的方法,计算了GaN、C单掺、Mg单掺和C-Mg共掺体系的电子结构和光学性质,计算结果表明:掺杂后,GaN体系的晶格发生畸变,有利于光生空穴-电子对的分离,C-Mg共掺体系结构最稳定,掺杂体系的禁带宽度均减小,其中C-Mg共掺体系的禁带宽度最小,在禁带中引入了杂质能级,说明掺杂可有效降低电子跃迁所需的能量.在光学性质方面,掺杂后,GaN在低能区介电峰和吸收峰均发生红移,且静介电常数增大;其中C-Mg共掺体系的对可见光的吸收最强,极化能力最强,因此C-Mg共掺将有望提高GaN在光催化性能和极化能力.     

MIT袋模型的一种束缚能跑动形式修正

最近,文献[1]在MIT袋模型的基础上引入了一种强耦合常数跑动形式和重夸克束缚能,较好地计算了所有已确认的基态强子谱。考虑到束缚能的贡献之一为重夸克间的短程束缚作用,即色电相互作用,其跑动形式将会取代之前的拟合参数。此跑动形式为类库仑势,随着袋半径R变化,并且在质量公式中参与变分。结果表明,色电相互作用的引入同样会将基态强子质量计算误差控制在大致40 MeV以内,且与拟合参数的方法相比得到了较为准确的结果。这为重夸克色电相互作用的研究提供了参考依据。     

A simple and effective boundary model in nonequilibrium molecular dynamics method

We propose a simple and effective boundary model in a nonequilibrium molecular dynamics (NEMD) simulation to study the out-of-equilibrium dynamics of polymer fluids. The present boundary model can effectively weaken the depletion effect and the slip effect near the boundary, and remove the unwanted heat instantly. The validity of the boundary model is checked by investigating the flow behavior of dilute polymer solution driven by an external force. Reasonable density distributions of both polymer and solvent particles, velocity profiles of the solvent and temperature profiles of the system are obtained. Furthermore, the studied polymer chain shows a cross-streaming migration towards center of the tube, which is consistent with that predicted in previous literatures. These numerical results give powerful evidences for the validity of the present boundary model. Besides, the boundary model can also be used in other flows in addition to the Poiseuille flow.     

Syntheses,Crystal Structures and Properties of Organic–Inorganic Hybrid Compounds of 4,4′-Bipyridine–Decorated Ni/Cu-Substituted Molybdophosphates

Organic–inorganic hybrid compounds of transition metal mono-substituted molybdophosphates, (H₂bipy)₂[PNi(Hbipy)Mo₁₁O₃₉]·4H₂O (1), (H₂bipy)_1.5[HPCu(Hbipy)Mo₁₁O₃₉]·4H₂O (2) (bipy = 4,4′-bipyridine), were synthesized hydrothermally and characterized by elemental analysis, IR spectroscopy, TGA, fluorescent spectroscopy, powder and single crystal X-ray diffraction methods. In 1 and 2 the transition metal atom (Ni and Cu) occupies one site of twelve molybdenum atoms of Keggin anion and combines a monoprotonated bipyridine molecular cation, Hbipy⁺, forming a 4,4′-bipyridine–decorated M-substituted molybdophosphate anion (M = Ni and Cu). In 1 two anions form a dimer through hydrogen bonds, in 2 the anions form a chain through hydrogen bonds. The dimers or the chains, H₂bipy²⁺ cations and lattice water molecules are connected by hydrogen bonds, giving supramolecular compounds. The two kinds of bipy molecules, coordinated and uncoordinated, in 1 and 2 give two emission peaks in their photoluminescent spectra.