孤对键弱化效应研究

在H_2O_2、N_2H_4、F_2分子中,O—O、N—N、F—F键的键长分别是0.148、0.148、0.144nm,虽比C_2H_6分子中的C—C键(0.154nm)短,但其σ键键能分别是146、160、155kJ/mol,却比C—C键能(365 kJ/mol)小约2.5倍,通常称这类原子的单键键能的反常现象为“孤对键弱化效应”。传统观点认为,半径很小的N、O、F等在化合时必须相当接近才能键合,孤对电子的排斥作用阻止了其相互接近,削弱了键能,降低了键的稳定性。显然,将这种削弱效应考虑为原子间效应是不合理的。本文用键参数图解法对“孤对键弱化效应”提出了合理的解释。     

Design of Second-Order Nonlinear Optical Molecules Exhibiting Improved Nonlinearity-Transparency Trade-off and Large Nonlinearity

The nonlinear second-order optical susceptibilities(β) of a series of multi-branched molecules with triphenylbenezene as π center have been calculated by means of a combination of intermediate neglect of differential overlap Hamiltonian with the configuration interaction(INDO/SDCI) method combined with sum-over-states expression(SOS) .the results show that the β values are increased by replacing benzene rings with thiophene rings in the branches,as well as by increasing the donating and accepting strength of the three terminal substituents.The properies of the intermolecular charge transfer were studied through the calculation of charge changes between the ground and the main excited states and the frontier orbitals of these molecules.The results also indicate that these molecules investigated here possess improved transparency-nonlinearity properties.     

酞菁锌的电子光谱和三阶非线性光学性质

用ＩＮＤＯ／ＳＤＣＩ方法研究了酞菁锌的电子结构，紫外－可见光谱，三阶三线性光学系数及其色散效应。发现由于酞菁锌中Ｚｎ（Ⅱ）对γ的贡献很小使酞菁锌与酞菁的＜γ＞几乎相等。根据我们的计算结构对此进行了合理的解释。     

Fabrication and Characterization of ZnO-Based Film Bulk Acoustic Resonator with a High Working Frequency

We report on the fabrication and characterization of a ZnO-based film-bulk acoustic-resonance device utilized as biosensor. The device has a multilayer structure which consists of piezoelectric element (Au/ZnO/Pt) and a Bragg-reflection-layer acoustic isolation consisting of multilayers of ZnO/Pt. Dielectric measurements have revealed that the device has a very high working frequency (up to -3.1 GHz), meaning that the device may have a higher sensitivity than the devices reported in the literature.     

二相流计算的一种差分算法

考虑两相流的力学行为,忽略相间的耗散作用,建立了Euler型的基本控制方程．状态方程采用刚性状态方程．基于Abgrall提出的准则,在流动区域内,对可压两相流提出了一个精度较高的Euler型数值方法,数值格式是Godunov型格式,对守恒型和非守恒型方程采用HLLC型和Lax-Friedrichs型近似Riemann解算器,引入了速度驰豫和压强驰豫过程来代替两相间的相互作用．在一维情形下给出数值算例,并且和Saurel的算例进行了比较,结果表明该算法不但精确而且稳定,且在间断处没有数值振荡．     

（二噻吩[3,2—b：3‘,2’—d]环戊烷—4—亚基）C60中的分子轨 …

在ＺＩＮＤＯ方法基础上，按完全态求和公式编制了计算分子二阶非线性光学系数β的程序。研究了（二噻吩「３，２－ｂ：３‘，２’－ｄ」环戊烷－４－亚基）Ｃ６０中的分子轨道相互作用，计算了该分子的电子光谱和二阶非线性光学系数β，前者与实验结果吻合较好，后者属于理论预测性质。     

基于无振荡中心格式求解非均匀道路上的多车种LWR交通流模型

将无振荡中心格式推广于多车种LWR交通流模型,给出了一种求解非均匀道路上模型的高分辨率数值方法.为保证格式无振荡,采用非线性限制器近似离散斜率.通量的离散微分可以按分量来近似,使得雅可比矩阵的计算都可以避免.方法具有形式简单、计算量小的优点.应用该方法对信号灯控制等问题进行数值模拟,验证了方法的稳定性和有效性.     

丙烯聚合负载型Ziegler-Natta催化剂的ESR研究

用ESR方法对MgCl₂负载的钛系Ziegier-Natta催化剂进行了研究,获得了分辩率较好的谱图,并结合前人的工作将信号的归属同钛原子在MgCl₂上的负载情况对应起来.同时考察了内外给电子化合物对ESR谱图的影响,探讨了它们可能的作用机理.     

On the Correlation between the Blue Shift of Hydrogen Bonding and the Proton Donor-Proton Acceptor Distance

It is demonstrated that in all types of hydrogen bonds (X—H…Y) there is a balance between the long-range attractive orbital interactions and short-range Pauli/nucleus repulsions. When the proton acceptor approaches the proton donor from distance, the hydrogen bonding energy becomes more negative at relatively large distance, goes through a minimum, and then starts to become less negative when the short-range repulsive forces come into effect.Meanwhile, the X--H bond length increases at relatively large distances, goes through a maximum and starts to shorten when the short-range repulsive forces come into effect. Whether the hydrogen bond is red or blue shifted is dictated by the energy minimum position. If at the energy minimum position the X—H bond length is shorter than that for the free monomer, the hydrogen bond is blue shifted and vice versa. Further studies demonstrate that the recent report about the correlation of C—H bond lengths with proton donor-acceptor distance in F3C—H…OH2 and F3C—H…Cl^- is not fully correct because the authors conducted an inappropriate comparison. Furthermore, it is shown for the first time that the Pauli/nucleus repulsion theory is applicable to the blue-shifted hydrogen bonds in the X—H…π complexes and the blue-shifted lithium bonds in the X—Li…Y complexes.