Theoretical study of stereodynamics for the N+H2/D2/T2 reactions

The effects of isotopic variants on stereodynamic properties for the title reactions have been investigated using a quasi-classical trajectory method based on the first excited state NH2（I^2A＇） potential energy surface [Li Y Q and Varandas A J C 2010 J. Phys. Chem. A 114 9644]. The forward–backward symmetry scattering of the differential cross section can be observed, which demonstrates that all these reactions follow the insertion mechanism. Three angle distribution functions P（θr）, P（φr）, and P（θr, φr） with different collision energies and target molecules H2/D2/T2 are calculated. It is shown that the product rotational angular momentum is not only aligned, but also oriented along the direction perpendicular to the scattering plane. The title reaction is mainly governed by the ＂in-plane＂ mechanism through the calculated distribution function P（θr, φr）. The observable influences on the rotational polarization of the product by the isotopic substitution of H/D/T can be demonstrated.     

Mechanical and thermodynamic properties of the monoclinic and orthorhombic phases of SiC_2N_4 under high pressure from first principles

First principles calculations are preformed to systematically investigate the electronic structures, elastic and thermodynamic properties of the monoclinic and orthorhombic phases of Si C2N4 under pressure. The calculated structural parameters and elastic moduli are in good agreement with the available theoretical values at zero pressure. The elastic constants of the two phases under pressure are calculated by stress–strain method. It is found that both phases satisfy the mechanical stability criteria within 60 GPa. With the increase of pressure, the degree of the anisotropy decreases rapidly in the monoclinic phase, whereas it remains almost constant in the orthorhombic phase. Furthermore, using the hybrid density-functional theory, the monoclinic and orthorhombic phases are found to be wide band-gap semiconductors with band gaps of about 2.85 e V and 3.21 e V, respectively. The elastic moduli, ductile or brittle behaviors, compressional and shear wave velocities as well as Debye temperatures as a function of pressure in both phases are also investigated in detail.     

对氯苯腈的双色共振双光子电离和质量分辨阈值电离光谱

本文利用双色共振双光子电离和质量分辨阈值电离光谱技术,研究了对氯苯腈分子第一电子激发态S₁和离子基态D₀的振动特征,确定了对氯苯腈分子S₁←S₀电子跃迁的激发能为35818±2 cm^–1,精确的绝热电离能为76846±5 cm^–1.对氯苯腈分子³⁵Cl和³⁷Cl两种同位素有相同的激发能和电离能以及相似的振动特征.采用高精度密度泛函方法,计算了对氯苯腈分子在中性基态S₀、第一电子激发态S₁、离子基态D₀的结构参数和振动频率,分析了电子激发和电离过程中对氯苯腈分子结构和振动频率的变化,并对激发态和离子基态的振动光谱进行了归属,振动光谱上的活性振动大多数是苯环平面内的弯曲振动.通过比较对氯苯酚、对氯苯胺、对氯苯甲醚、对氯苯腈与苯酚、苯胺、苯甲醚、苯腈分子的跃迁能,分析了取代基Cl原子与苯环之间的相互作用及其对分子跃迁能的影响.     

抗压桩与抗拔桩侧阻的研究

对抗压桩和抗拔桩的桩侧摩阻力进行了理论探讨 ,从定量上考虑了桩周土的剪胀性及主应力方向旋转对侧阻的影响 ,得到了相应的影响系数和侧阻的预测公式.     

求解第一类Fredholm积分方程的一种新的正则化算法

应用一种新的正则化方法建立了一类新的求解第一类Fredholm积分方程的正则化算法, 并借助Matlab软件给出了数值算例.数值结果与理论分析基本一致,而且表明文中建立的正则化比通常的Tikhonov正则化更精确.     

两个安全第一思想模型的比较分析

针对投资者可能的投资需求确立了基于安全第一思想下两个相近的投资目标:1、极大化投资末期总收益率超过给定水平α的概率;2、极小化投资末期总收益率与给定水平α的距离.并分别就这两个目标建立了优化决策模型,得到了模型解析解,最后对两个模型结果进行了比较分析和经济解释.     

First-Principles Calculations of Elastic Constants of Superconducting MgB2

The five independent elastic constants of superconducting MgB2 are obtained using the first-principles plane wave method with the new relativistic analytic pseudopotential of the Hartwigsen-Goedecker-Hutter (HGH) scheme in the frame of local density approximation. The dependences of bulk modulus on temperature and pressure are also obtained. It is suggested that the HGH-type pseudopotentials are successful in investigating the ground-state mechanical properties of any solids.     

世界珠算心算联合会第一届理事会工作报告

我荣幸的代表世界珠算心算联合会第一届理事会，向各位会员报告本届理事会的工作，请审议。     

First-Principles Calculation of Static Equation of State and Elastic Constants for GaSe

The all-electron full potential augmented plane-wave plus local orbital （APW_Io） method with the local-density approximation （LDA） is used to calculate the static equation of state （EOS） and elastic constants of crystalline GaSe. After the full relaxation of atomic positions, the calculated band structure at ambient pressure is consistent with the experimental data to the extent expected to give the known limits of LDA one-electron energies. The equilibrium lattice parameters found here exhibit the usual LDA-induced contraction. However, constrained with the experimental cell volume, the interlayer separation exhibits an expansion due to the LDA underestimate of the weak interlayer bonding. The calculated values of elastic constants are in good agreement with acoustic measurements. The pressure derivatives of the lattice constants derived from the theoretical elastic constants are in very good agreement with x-ray spectra measurements. Two analytical EOSs have been determined at pressures up to 4.5 GPa. The pressure evolution of the structure indicates that the layer thickness decreases slightly under pressure.