Au/Pd(111)双金属表面催化噻吩加氢脱硫的反应机理

采用密度泛函理论（DFT）计算了Pd（111）表面含有N（N=1-4）个Au原子数目时的表面形成能,选取最优构型进一步研究了噻吩在Au/Pd（111）双金属表面的吸附模式及加氢脱硫反应过程. 结果表明：当Pd（111）表面含有1个Au原子时,其形成能最低. 在Au/Pd（111）双金属表面噻吩初始吸附于Pd-Hcp-30°位时,其构型最稳定. 在各加氢脱硫过程中,反应总体均放出热量. 对于直接脱硫机理,其所需活化能较低,但脱硫产物较难控制;对于间接脱硫机理,反应最有可能按照顺式加氢方式进行,C―S键断裂开环时所需活化能最高,是反应的限速步骤. 此外,与单一Au（111）面及Pd（111）面相比,Au/Pd（111）双金属表面限速步骤的反应能垒最低,表明AuPd双金属催化剂比Au、Pd单金属催化剂更有利于噻吩加氢脱硫反应的进行.     

Periodic and chaotic oscillations in mutual-coupled mid-infrared quantum cascade lasers

Dynamic states in mutual-coupled mid-infrared quantum cascade lasers (QCLs) were numerically investigated in the parameter space of injection strength and detuning frequency based on the Lang—Kobayashi equations model. Three types of period-one states were found, with different periods of injection time delay τ_inj, 2τ_inj, and reciprocal of the detuning frequency. Besides, square-wave, quasi-period, pulse-burst and chaotic oscillations were also observed. It is concluded that external-cavity periodic dynamics and optical modes beating are the mainly periodic dynamics. The interaction of the two periodic dynamics and the high-frequency dynamics stimulated by strong injection induces the dynamic states evolution. This work helps to understand the dynamic behaviors in QCLs and shows a new way to mid-infrared wide-band chaotic laser.     

Multiparty Quantum Secret Sharing of Key Using Practical Faint Laser Pulses

Based on a bidirectional quantum key distribution protocol [Phys. Rev. A 70 (2004)012311], we propose a (m-1, m-1)-threshold scheme of m (m≥3)-party quantum secret sharing of key by using practical faint laser pulses. In our scheme, if all the m-1 sharers collaborate, they can obtain the joint secret key from the message sender. Our scheme is more feasible according to the present-day technology.     

液固界面的1,9—二苯基—1,3,6,8—壬四烯—5酮分子的STM研究

对于固液界面分子行为的研究在以下几个方面有着重要意义,如对润滑和吸附的更深入的了解、液晶在表面的取向、界面的分子的识别现象、催化、电荷及物质在超薄有机层中的传输等。从理论角度来说,单分子层的有序性也是人们非常感兴趣的课题。扫描隧道显微镜(STM)是80年代初发展起来的一种新型表面分析工具,对于单分子     

Lien元素簇合物的成键作用

镇元素簇合物是人们最感兴趣的簇合物之一l‘－’］．已有的。作主要是研究它的稳定性和电子结构，对其成键性质还研究得不多·为止匕我们对Lkin为元素簇合物中所含原子个数，e为该化合物的电荷）进行了定域化研究，并得出一些有意义的结果·1计算我4rl采用GAMESS90程序m，在4－31G基组下进行了正则分子轨道SCFi十算（闭壳层采用RHF，开壳层采用UHF）．然后，以QSU90程序问，用B0yS方法进行了定域化计算，得到定域分子轨道（LM），再根据LMO的系数和集居数分析，判断各分子中原子的成键情况问．共计算了18个簇合物．它们的原子数…     

Elastic bag model for molecular dynamics simulations of solvated systems: application to liquid water and solvated peptides

The fluctuating elastic boundary (FEB) model for molecular dynamics has recently been developed and validated through simulations of liquid argon. In the FEB model, a flexible boundary which consists of particles connected by springs is used to confine the solvated system, thereby eliminating the need for periodic boundary conditions. In this study, we extend this model to the simulation of bulk water and solvated alanine dipeptide. Both the confining potential and boundary particle interaction functions are modified to preserve the structural integrity of the boundary and prevent the leakage of the solute-solvent system through the boundary. A broad spectrum of structural and dynamic properties of liquid water are computed and compared with those obtained from conventional periodic boundary condition simulations. The applicability of the model to biomolecular simulations is investigated through the analysis of conformational population distribution of solvated alanine dipeptide. In most cases we find remarkable agreement between the two simulation approaches.     

Ligand-promoted solvent-dependent ionization and conformational equilibria of Re(CO)3Br[CH2(S-tim)2] (tim = 1-methylthioimidazolyl). Crystal structures of Re(CO)3Br[CH2(S-tim)2] and {Re(CO)3(CH3CN)[CH2(S-tim)2]}(PF6)

The compounds Re(CO)3Br[CH2(S-tim)2] (1) and {Re(CO)3(CH3CN)[CH2(S-tim)2]}(PF6) (2), where tim is 1-methylthioimidazolyl, were prepared in high yields and characterized both in the solid state and in solution. The solid-state structures show that the ligand acts in a chelating binding mode where the eight-member chelate ring adopts twist-boat conformations in both compounds. A comparison of both solid-state IR data for CO stretching frequencies and the solution-phase voltammetric measurements for the Re(1+/2+) couples between 1, 2, and related N,N-chelates of the rhenium tricarbonyl moiety indicate that the CH2(S-tim)2 ligand is a stronger donor than even the ubiquitous dipyridyl ligands. A combination of NMR spectroscopic studies and voltammetric studies revealed that compound 1 undergoes spontaneous ionization to form {Re(CO)3(CH3CN)[CH2(S-tim)2]+}(Br-) in acetonitrile. Ionization does not occur in solvents such as CH2Cl2 or acetone that are less polar and Lewis basic (less coordinating). The equilibrium constant at 293 K for the ionization of 1 in CH3CN is 4.3 x 10(-3). The eight-member chelate rings in each 1 and 2 were found to be conformationally flexible in all solvents, and boat-chair conformers could be identified. Variable-temperature NMR spectroscopic studies were used to elucidate the various kinetic and thermodynamic parameters associated with the energetically accessible twist-boat to twist-boat and twist-boat to boat-chair interconversions.     

高岭石/苯甲酰胺插层复合物的热分解行为及脱嵌反应动力学

以高岭石/二甲基亚砜为前驱体,利用置换法制备了高岭石/苯甲酰胺插层复合物。XRD和FTIR分析表明苯甲酰胺进入高岭石层间并与其形成新的氢键。采用TG、DSC研究了插层复合物的热分解行为。结果表明复合物在加热过程中发生两步分解,第一步是插层复合物的分解,即插层剂分子于231℃发生脱嵌,第二步为高岭石脱羟基的过程。针对第一阶段的脱嵌反应,采用等转化率法改进后的迭代法、Malek法以及Dollimore法等动力学方法计算得到了完整的动力学三因子:活化能Ea=75.4kJ.mol-1,指前因子A的范围为4.9×1010~8.8×1010s-1,动力学方程为:G(α)=[1-(1-α)1-n]/(1-n),f(α)=(1-α)n。     

Pt表面修饰WO3纳米线薄膜对高浓度氢气传感性能的研究

本文采用热蒸发法合成了高结晶度的WO3纳米线薄膜,并利用溅射法把Pt纳米颗粒催化剂均匀溅射到纳米线的表面,形成Pt表面修饰WO3纳米线的复合纳米网络结构.气敏传感性能测试结果表明,在工作温度为100～140℃,Pt表面修饰的WO3纳米线薄膜对高浓度氢气具有响应度高(电阻变化率接近100;)、响应时间短(小于1.0s)、可重复性好等特点,能够有效地降低传感器的工作温度,解决高浓度探测时的饱和和失效问题,在工业生产中具有潜在的应用价值.     

非球面检测中最佳入射球面波和最佳参考球面波的确定

为了能够对非球面光学元件面型进行高精度的干涉检测,提出了一种确定最佳入射球面波和最佳参考球面波的新方法。该方法通过计算分析入射球面波与非球面反射波干涉条纹密度,确定最佳入射球面波的波源位置;通过计算分析在干涉图记录平面CCD上干涉条纹的密度,确定非球面检测时参考球面波波源的最佳位置。应用该理论与方法,不仅可明确非球面检测时CCD等光路元件选型的具体策略,而且可用于指导非球面检测调试过程,并能够通过对干涉图的深入分析,获得更多被测非球面的信息。