氧化镁表面修饰稀土催化材料的制备和气敏性能

本文采用湿化学过程的柠檬酸络合法、可控化学沉淀法和溶胶-凝胶法合成了纳米复合金属氧化物LaFeO3,利用各种分析方法对材料的物性和结构进行了分析和表征;并测定了材料对氧化性气体和还原性气体的气敏性能．研究结果表明LaFeO3复合物对NO2在350℃灵敏度高达127．83,特别通过添加MgO对基材进行表面修饰灵敏度提高到845．37,约添加前的70倍．本文还进一步考察了添加质和添加量对基材的结构和气敏性能的影响,并通过研究材料表面对气体的吸脱附性能和元素电子结合能的变化对敏感作用机制进行了深入分析和探讨．     

SCN——BrO3——H+体系的非线性动力学行为

＄酸盐驱动的振荡器，特别是Belousov－Zhabotinskii反应［‘1及其变种是研究得最为广泛、最为透彻的均相化学振荡反应．但两组份非催化的漠酸盐振荡器还只是近年来才发现开始研究的·含硫化合物如SC（NH。）。，SO3－，SCN一等非催化滇酸盐振荡器的非线性行为逐渐成为研究热点     

钴膦基元化合物的电化学行为

近年来，随着硫、脚混配配位化学的迅猛发展，有机卿参与的过渡金属流基化合物正在受到越来越多的重视［‘，’］．有机磷的参与增加了金属硫基配合物的多样性，推动了金属流基配位体系的合成化学和结构化学的发展．Co（PPh3hCI。和Co（PPha）aCI（PPh。为三苯基磷）是重要的含     

In3+与Ga3+对纯铝在KOH溶液中电化学行为的影响

通过极化曲线、交流阻抗的方法研究了纯给在1mol·L－1KOH溶液中的电化学行为，分析了铝在碱性介质中活性溶解时的特殊动力学现象．通过溶液中添加金属离子In3十和Ga3＋，研究了高析氢过电位金属离子对纯铝在KOH溶液中阳极溶解过程的影响机制，并结合扫描电镜照片（SEM）证明了In3十和Ga3十对铝电极溶解的影响过程．     

F+HC≡CH→HC≡C+HF反应的理论研究

在大气化学和燃烧历程的研究中，只含两个碳原子的碳氢化合物自由基的研究占有很重要的地位．乙炔与氟原子的反应是实验室制取HCZC·自由基的重要方法．因此乙炔与氟原子的反应在动力学研究中一直很受重视．乙炔与氟原子的反应存在有以下三种反应方式问：门抽取反应：F＋C。H。     

CH3+HNCO反应机理的理论研究

异氰酸(HNCO)分解引发的一系列自由基反应是氮氧化物快速消除机理[1,2](RAPRENOX)所研究的领域,该反应涉及到燃烧化学中氮氧化物NOX的消除,所以获得这些反应准确的位垒就成为实验化学和理论化学所要解决的问题。本文中我们重点研究CH3+HNCO反应机理,探讨CH3自由基是否也能象氮氢自由基一样,在异氰酸(HNCO)分解反应中起作用。1　计算方法用量子化学MP2方法,在6 311++G 水平上计算了CH3自由基与HNCO反应的反应物、产物、中间体和过渡态的几何构型,用QCISD(T)方法在6 311++G 水平上计算了它们的能量。通过振动分析确定…     

Ca1-xZnxTiO3:Pr3+的固溶特性及其发光性能

通过高温固相合成法制备了名义组成为Ca1-xZnxTiO3：Pr^3＋（x=0．0～0．20）的红色发光材料，采用XRD和光谱等手段研究微量Zn掺杂的单相Ca1-xZnxTiO3：Pr^3＋材料的晶体结构参数与发光性能，分析了等价Zn^2＋的掺杂对固溶体结构参数与发光性能的影响规律。结果表明，在x≤0．01微量Zn掺杂时，Zn取代Ca形成单相Ca1-xZnxTiO3：Pr^3＋固溶；其晶胞参数和晶胞体积，260和330nm两激发带以及610nm发射峰强度均随Zn掺量增加快速减小，且发光强度与晶胞参数的变化规律相吻合。分析表明这种变化与Zn取代Ca形成的固溶结构有关。     

SiO2在CH3ONO→CH3O+NO解离中作用的理论研究

利用B3LYP方法,在6-31 G^ 基组下研究了在SiO2存在下的CH3ONO→CH3O NO解离反应．计算了全优化下的解离反应,以及固定SiO2的键长和键角做部分优化下的解离反应．在反应中SiO2与CH3ONO相接近,O-N键逐渐伸长,生成复合物,放出热量,进一步促进了CH3ONO中NO的解离．     

用电化学方法研究微过氧化物-8与Eu3+作用位点

循环伏安法;用电化学方法研究微过氧化物-8与Eu3+作用位点     

3+X高考改革对地方高校学生化学学习影响的调查与对策

对广东3+X高考改革5年来,地方高校化学专业课程教学质量的影响进行了调查与分析.调查结果表明,学生在中学时是否选修化学科目,进入大学学习化学专业课程期间,在专业知识学习和心理方面表现出较大的差异.本文探讨了减少这种差异的方法,提出了全面提高化学教学质量的对策.     

α-Pb(N_3)_2晶体的周期性从头计算

叠氮化铅是最常用的起爆剂。对α-Pb(N_3)_2晶体首次进行ab initio周期性 计算,求得其能带和电子结构,探讨了结构、性能关系。原子间重叠布居和电荷密 度分析表明,铅离子与叠氮根离子末端氮原子(N_T)间的轨道重叠作用较强,部分 电子已从叠氮根转移到铅离子。经基组叠加误差(BSSE)较正求得α-Pb(N_3)_2的晶 格能为-2187.35 kJ/mol,与源自实验的文献值吻合。晶体前沿占有轨道主要由叠 氮根端位氮(N_T)的原子轨道(AO)组成,而前沿空轨道则主要由Pb~(2+)的AO组成, 这有助于N_T上电子直接向金属离子跃迁;根据“（电子）最易跃迁原理（PET）” 可预测α-Pb(N_3)_2的感度较大,适合于作起爆药使用。     

A Theoretical Study of the Mechanism for the Photodecomposition of AgN3

IntroductionOrganic and inorganic azides have been an extensive investigated subject for manyyears['J. Azide compounds as the energetic materials have also been studied and character-ized[2], however, the kinetic characters have unsufficiently been studied in theory and experi-ment. In the 1930's it was discovered that the slow thermal decomposition of NaN3, KN3,AgNs and Pb(N,)2 was accompanied by very feeb1e 1uminescence, Which has been claimed tobe independent of the cations[3J, and coul…     

Periodic DFT approach to benzotrifuroxan crystal

Density Functional Theory (DFT) calculations at the B3LYP/6‐21G* level were performed on crystalline benzotrifuroxan (BTF). The frontier bands are generally quite flat. The energy gap between the highest occupied crystal orbital (HOCO) and the lowest unoccupied crystal orbital (LUCO) is 3.89 eV, indicating that the crystal is an electrical insulator. All the atoms of BTF make up both the lower and the higher energy bands. The projection of density of state (DOS) indicates that there exists no region with much higher reactivity as other explosives, since the coplanar rings of BTF are conjugated. An anisotropic impact on the bulk makes the electron transfer from carbon atoms to nitrogen and oxygen atoms, which lowers the strength of the C–C bond. The crystal lattice energy is predicted to be –47.39 kJ/mol. The elastic constants C₁₁, C₂₂, and C₃₃ are predicted to be 191.48 GPa, 94.39 GPa, and 347.42 GPa, respectively. The large differences of C₁₁, C₂₂, and C₃₃ indicate the anisotropic properties of BTF upon impacting. © 2004 Wiley Periodicals, Inc. Int J Quantum Chem, 2005     

Waugh-型镍钼杂多酸的量子化学计算

采用半经验INDO法，完成了Waugh-型镍钼杂多酸（NH44）6〔NIMO9O32〕·6H2O的量子化学计算，得到146个成键轨道和78个反键轨道，轨道能级，电荷和键序等数据。通过对这些数据的分析，表明杂多酸分子中端氧和Ni都可能为化学活性中心，各原子轨道在分子轨道中都占有一定比例，其HOMO和LUMO能级皆为负值，其体系具有进一步接受电子的能力。这些结论与实验事实一致。     

图解中心原子轨道的杂化方式

借助图形方法,分析了不同常见几何构型分子中心原子轨道杂化方式的原因——与端基原子轨道的有效重叠,利用中心原子价层轨道的能量接近度的判断,决定最终可能的杂化方式。     

Copper and silver complexes containing organic azide ligands: syntheses, structures, and theoretical investigation of [HB(3,5-(CF3)2Pz)3]CuNNN(1-Ad) and [HB(3,5-(CF3)2Pz)3]AgN(1-Ad)NN (where Pz = pyrazolyl and 1-Ad = 1-adamantyl)

Treatment of [HB(3,5-(CF3)2Pz)3]Na(THF) with CF3SO3Cu followed by 1-azidoadamantane affords [HB(3,5-(CF3)2Pz)3]CuNNN(1-Ad) in 65% yield. The solid state structure shows that the copper atom is coordinated to the terminal nitrogen atom (NT) of the azidoadamantane ligand. The related silver(I) adduct can be prepared in 80% yield by the treatment of [HB(3,5-(CF3)2Pz)3]Ag(THF) with 1-azidoadamantane. However, [HB(3,5-(CF3)2Pz)3]AgN(1-Ad)NN shows a different bonding mode where the silver atom coordinates to the alkylated nitrogen atom (NA) of the azidoadamantane ligand. Asymmetric stretching bands of the azido group for copper and silver adducts appear at 2143 and 2120 cm-1, respectively. Theoretical investigation shows that steric effects do not play a dominant role in determining the bonding mode of the azide ligand in these two metal complexes. Although the copper(I) ion affinity for the two coordinating sites NT and NA is nearly identical, copper-azide back-bonding interactions favor the copper-NT mode of bonding over the copper-NA mode. Silver (a very poor back-bonding metal) prefers the NA site for coordination. The NA site has a significantly higher proton affinity and slightly higher sodium ion affinity. Important structural parameters for [HB(3,5-(CF3)2Pz)3]CuNNN(1-Ad) and [HB(3,5-(CF3)2Pz)3]AgN(1-Ad)NN are as follows: Cu-NT 1.861(3) A, NT-N 1.136(4) A, N-NA 1.219(4) A, NT-N-NA 173.1(3) degrees; Ag-NA 2.220(5) A, NT-N 1.143(12) A, N-NA 1.227(10) A, NT-N-NA 176.8(12) degrees. Overall, the azidoadamantane ligand does not undergo any significant changes upon coordination to Cu(I) or Ag(I) ions.     

Crystal structure and chemical bonding of the high-temperature phase of AgN3

The crystal structure of silver azide (AgN3) in its high-temperature (HT) modification was determined from X-ray powder diffraction data, recorded at T = 170 degrees C and was further refined by the Rietveld method. The structure is monoclinic (P21/c (No. 14), a = 6.0756(2) A, b = 6.1663(2) A, c = 6.5729(2) A, beta = 114.19(0) degrees, V = 224.62(14) A3, Z = 4) and consists of two-dimensional Ag and N containing layers in which the silver atoms are coordinated by four nitrogen atoms exhibiting a distorted square coordination environment. These sheets are linked together by weaker perpendicular Ag-N contacts, thus forming a 4 + 2 coordination geometry around the silver atoms. The phase transition has been characterized by DTA, DSC, and measurement of the density, as well as of the ionic conductivity. Both, the room-temperature and the HT phase are electrically insulating. This fact is getting support by DFT band structure calculations within the generalized gradient approximation, using the PBE functional. On the basis of the DFT band structure, the bonding characteristics of both phases are essentially the same. Finally, the implication of the existence of a low-symmetry HT-phase in a crystalline explosive concerning decomposition mechanisms is discussed.     

Computational study of analogues of the uranyl ion containing the -N=U=N- unit: density functional theory calculations on UO2(2+), UON+, UN2, UO(NPH3)3+, U(NPH3)2(4+), [UCl4[NPR3]2] (R = H, Me), and [UOCl4[NP(C6H5)3]

The electronic and geometric structures of the title species have been studied computationally using quasi-relativistic gradient-corrected density functional theory. The valence molecular orbital ordering of UO2(2+) is found to be pi g < pi u < sigma g < sigma u (highest occupied orbital), in agreement with previous experimental conclusions. The significant energy gap between the sigma g and sigma u orbitals is traced to the "pushing from below" mechanism: a filled-filled interaction between the semi-core uranium 6p atomic orbitals and the sigma u valence level. The U-N bonding in UON+ and UN2 is significantly more covalent than the U-O bonding in UON+ and UO2(2+). UO(NPH3)3+ and U(NPH3)2(4+) are similar to UO2(2+), UON+, and UN2 in having two valence molecular orbitals of metal-ligand sigma character and two of pi character, although they have additional orbitals not present in the triatomic systems, and the U-N sigma levels are more stable than the U-N pi orbitals. The inversion of U-N sigma/pi orbital ordering is traced to significant N-P (and P-H) sigma character in the U-N sigma levels. The pushing from below mechanism is found to destabilize the U-N f sigma molecular orbital with respect to the U-N d sigma level in U(NPH3)2(4+). The uranium f atomic orbitals play a greater role in metal-ligand bonding in UO2(2+), UN2, and U(NPH3)2(4+) than do the d atomic orbitals, although, while the relative roles of the uranium d and f atomic orbitals are similar in UO2(2+) and U(NPH3)2(4+), the metal d atomic orbitals have a more important role in the bonding in UN2. The preferred UNP angle in [UCl4(NPR3)2] (R = H, Me) and [UOCl4(NP(C6H5)3)]- is found to be close to 180 degrees in all cases. This preference for linearity decreases in the order R = Ph > R = Me > R = H and is traced to steric effects which in all cases overcome an electronic preference for bending at the nitrogen atom. Comparison of the present iminato (UNPR3) calculations with previous extended Hückel work on d block imido (MNR) systems reveals that in all cases there is little or no preference for linearity over bending at the nitrogen when R is (a) only sigma-bound to the nitrogen and (b) sterically unhindered. The U/N bond order in iminato complexes is best described as 3.     

First-principles study of structural and vibrational properties of crystalline silver azide under high pressure

A detailed first-principles study of the structural and vibrational properties of crystalline silver azide under hydrostatic pressure of 0–500 GPa has been performed with density functional theory in the generalized gradient approximation. The crystal structure is relaxed to allow ionic configurations, cell shape, and volume to change without any symmetry constraints. It is found that the silver azide crystal remains orthorhombic structure with Ibam space group for pressures up to 7 GPa, where there is a transition to an I4/mcm tetragonal symmetry. The lattice parameter and electronic structure are investigated as functions of pressure. The calculated vibrational frequencies at ambient pressure are in agreement with available experimental data. We also discuss the pressure-induced frequency shifts for the internal and lattice modes of silver azide crystal upon compression.     

Interaction of metallic nanoparticles with a biologically active molecule, dopamine

We present the results of first-principles molecular orbital calculations describing the interaction of metallic nanoparticles, represented by Mn(13), Ag(13), and Al(13) atomic clusters, with a biologically active molecule, dopamine. The interaction strength, determined in terms of the nanoparticle-molecule complex binding energy, is found to be higher for Mn than either Ag or Al and can be explained in terms of the degree of the hybridization of the (metal) atomic orbitals with the molecular orbitals in the complex. Furthermore, smaller interaction strength of these metallic nanoparticles with water compared to that with dopamine predicts the preference of forming a complex of dopamine with the metallic nanoparticles in the aqueous solution. The calculated results may therefore suggest that the presence of these metallic nanoparticles could induce different levels of dopamine depletion in solution.