氘代甲烷几何构型及物性的量子化学研究

用HF/6-31G^**、密度泛函方法B3LYP/31G^**、二级微扰MP2/6-31G^**、四级微扰MP4/6-31G^**方法对甲烷和氘代甲烷进行几何构型全优化,并将优化的结果与实验值进行比较.用上述4种方法对甲烷和氘代甲烷分子进行分子的振动基频计算.密度泛函、二级微扰、四级微扰优于HF/6-31G^**,尤其是密度泛函、四级微扰方法.密度泛函方法所用的机时远小于微扰方法.不同方法计算所得的氘代甲烷振动频率值与实验值的最大误差为10.4%,最小误差为2.0%.     

利用自洽平均值近似法巧解非线性谐振子问题

利用自洽平均值近似方法计算了带坐标3次方项和带坐标4次方项的非线性谐振子的能量本征值,并且分别与微扰近似方法求得的结果相对比,在小参数的情况下,其结果比微扰近似方法误差更小、更精确.     

原子受激跃迁的非微扰解法

介绍了新近发展的求解原子在弱电磁波扰动下的受激跃迁的非微扰方法,详细计算并讨论了一种特殊情况.非微扰结果在微扰条件下退化为含时微扰论的结果,但克服了后者在近共振区明显不合理的缺陷.根据非微扰结果,电偶极跃迁的选择定则在短时间内近似成立,但长时间后禁戒跃迁的概率与允许跃迁可相比拟.     

参数微扰法计算氦原子基态能量

根据参数微扰法理论,选择有效核电荷数为z*=2-σ的两个类氢原子的ns态的波函数的组合,作为氦原子基态的1级至4级近似波函数.应用参数微扰法计算了氦原子基态4级近似能量.计算结果表明参数微扰法得到的氦原子基态4级近似能量与实验值的误差为ΔE=0.004922028e_s~2/a_0.     

带肋通道和气膜冷却交互下的绝热和耦合传热研究

燃气轮机透平叶片冷却中,内部肋片扰流对气膜冷却效果有显著影响,当边界条件为金属壁面绝热和金属壁面耦合时,冷却效率会有不同的表现。本文采用数值计算方法,分别计算绝热边界和耦合边界条件下,气膜孔进口与内部冷却扰流肋片不同相对位置条件下的绝热气膜冷却效率和耦合条件下的整体冷却效率进行计算。结果表明当气膜进口位于肋后扰流区时,绝热气膜冷却效率较差。绝热边界和耦合边界条件下流场相似,气膜孔与肋片相对位置对于气膜孔下游整体冷却效率的影响与绝热条件相似。     

有效折射率微扰法研究单缺陷光子晶体平板微腔的性质

应用有效折射率微扰法结合二维/三维平面波方法研究了施主和受主缺陷型H1微腔的性质, 使用修正后的有效折射率可以准确地计算微腔的腔模频率, 与三维全矢量时域有限差分法的计算结果很相近. 对于施主型H1微腔, 以介质带边为匹配标准修正的有效折射率计算的微腔腔模频率误差最小, 而对于受主型H1微腔, 匹配标准则应设置为中间带. 有效折射率微扰法既可以将计算的维度从三维降到二维, 大大减少计算所需的计算机内存和时间, 又可以保持计算结果的准确性, 这对于光子晶体微腔的广泛应用具有非常重要的价值.     

强耦合Schrdinger方程的近似解析解法

分析了用李政道等人的方法求解强耦合Schr dinger方程的适用条件 ,具体计算了汤川势问题及相应的微扰问题 .     

考虑非常数自旋扭矩时LLS方程的微扰解

不将自旋扭矩因子近似为一个常数,利用Melnikov微扰方法推导了LLS方程解的表达式,通过VC与MATLAB混和编程进行计算,计算结果显示,与将自旋扭矩因子视为常数的情况相比较,自旋扭矩为磁化强度函数时的磁化强度运动轨道在离开未扰轨道初期仅在未扰轨道附近做微小振动,在翻转时刻附近有较大振荡,并且所预言的磁化强度翻转时刻相对提前. 关键词： 自旋扭矩 磁化强度 LLS方程 微扰     

弱光场中氢原子的稳定性

虑一个处在弱光场中的经典氢原子系统,运用直接微扰方法求出了该系统微扰解的一般形式,并给出了解有界的条件。分析结果表明,在一般情况下,氢原子的微扰解是无界的,因而系统是Lyapunov不稳定的,但在解有界的条件满足时,系统则是Lyapunov稳定的。     

短路金属栅对正入射瑞利波的散射

由压电晶体动力学方程等出发,用电表面边界微扰技术得到了入射声表面波在栅区激发的微扰电场及电荷分布;将这些电荷作为表面激发源,用积分变换得到了包括散射声表面波和体波的一般积分解。数值计算了YZ-LiNbO_3,表面上短路金属栅对正入射瑞利波散射的声表面波,给出了其反射系数,前向散射系数等与栅条宽度的关系;进而导出了声表面波经过金属栅时的相速变化。理论计算与实验测量结果符合较好。     

稠苯芳杂环及其烷基质子化学位移的计算

本文提出了予测稠苯芳杂环及其烷基链上质子化学位移的计算方法。 将稠苯芳杂环化合物用凯库勒式表示,计算式为为需考虑的苯环内的乙烯基效应。σ_mi,ci为各苯环的环流效应。σ_1,Hc为各芳杂环的屏蔽效应,对杂环上质子它就是该单独芳杂环上相应质子的δ值,对苯环上质子要将它分解为各结构因素的效应,即:σ_1,He=(1/2)^d-1δ_x=y(或σ_z)+σ_c-c·σ_m,H. σ_x-y与σ_z为杂原子或其基团的屏蔽效应,σ_c=c为存在于芳杂环中的乙烯基的效应,σ_m,Hc为芳杂环的环流效应,d为对不同质子所考虑的键数。有取代基时需考虑取代基的效应。计算环上烷基质子的公式为:δ=σ_p,CH3+ασ_c,CH3+βσ_t,CH3+σ_l,G σ_l,G为稠苯芳杂环基的某级效应。     

Structural phase transitions at clean and metal-covered Si(111) surfaces investigated by RHEED spot analysis

Structural phase transitions between various kinds of superlattice structures formed on a Si(111) surface have been investigated by spot analysis of reflection high-energy electron diffraction (RHEED). Reversible transitions induced by temperature changes and irreversible ones induced by metal depositions were observed. Detailed discussions on the dynamics of the phase transitions are made by quantitative analyses of integrated spot intensity and profile. For a phase transition of 7′7  1′1 structures on a clean Si(111) surface, a hysteresis with temperature difference of 5°C. between in heating and cooling processes was found in the spot intensity change, indicating a first-order transition. Hysteresis was hardly recognized, on the other hand, for transitions of Au-induced superstructures (5×2-Au or ×-Au)  1×1-Au. The spot profiles were found to be broadened during the transition of Si(111)-×-Au  1×1-Au, which was a signature of a continuous transition, while the profiles remained unchanged during the transitions of the 7×7  1×1 and 5×2-Au  1×1-Au phases. Structural conversions induced by In adsorption on the Si(111) surface kept at constant temperatures were also analyzed. The conversions at room temperature were totally dependent on the initial substrate surface structures; the 7×7 surface did not show any structural conversion with In adsorption, while the ×-In surface successively converted to a 2×2 and a × phase with coverage increase. The structural transitions at elevated temperatures were sensitively dependent on the temperatures. Sequences of transitions among the 7×7, 4×1, ×, 1×, and ×4 were quantitatively revealed as changes in RHEED spot intensity.     

ErP5O14非晶玻璃的红外量子剪裁

研究了Er_1.0P₅O₁₄铒非晶玻璃的红外量子剪裁现象. 从吸收谱和激发光谱的计算比较中肯定了Er_1.0P₅O₁₄非晶 玻璃的1537.0 nm红外荧光为多光子量子剪裁荧光. 从Er_1.0P₅O₁₄非晶玻璃的可见和红外荧光发射光谱中发现激发²H_11/2, ⁴G_11/2和⁴G_9/2能级所导致的⁴I_13/2→⁴I_15/2量子剪裁红外荧光很强;基于自发辐射速率、无辐射弛豫速率和能量传递速率等参数的计算,对其量子剪裁机理进行了分析.发现起源于基态的强下转换能量传递{²H_11/2→⁴I_9/2,⁴I_15/2→⁴I_13/2},{⁴G_11/2→⁴I_13/2, ⁴I_15/2→²H_11/2},{⁴G_9/2→⁴F_7/2,⁴I_15/2→⁴I_13/2}和{⁴G_9/2→⁴I_13/2, ⁴I_15/2→²H_11/2}是导致Er_1.0P₅O₁₄非晶玻璃具有强的三光子和四光子量子剪裁红外荧光的原因.研究结果对改善太阳能电池效率有一定意义.     

1-forms over the moduli space of irreducible connections defined by the spectrum of Dirac operators

Let (P) be the moduli space of irreducible connections of a G-principal bundle P over a closed Riemannian spin manifold M. Let D_A be the Dirac operator of M coupled to a connection A of P and f a smooth function on M. We consider a smooth variation A(u) of A with tangent vector ω and denote T_ω:= (D_A(u)−f) (u=0. The coefficients of the asymptotic expansion of trace (T_ω · e^-t(D_A−f)2) near t=0 define 1-forms a^(k)_f, K=0, 1, 2, … on (P). In this paper we calculate aa⁽⁰⁾_f, a⁽¹⁾_f, a⁽²⁾_f and study some of their properties. For instance using the 1-form a⁽²⁾_f for suitable functions f we obtain a foliation of codimension 5 of the space of G-instantons of S⁴.     

Phase formation and magnetic properties of Nd2Fe14B-type Nd16Co76B8−xCx alloys and their hydrides

An attempt is made to synthesize Nd₂Co₁₄C compound by mechanical alloying Nd₁₆Co₇₆B_8−xC_x (0x8) alloys and subsequent annealing. Phase formation and magnetic properties of Nd₂Fe₁₄B-type Nd₁₆Co₇₆B_8−xC_x alloys and their hydrides are investigated. The Nd₂Co₁₄(B,C) phase with Nd₂Fe₁₄B-type structure is formed for Nd₁₆Co₇₆B_8−xC_x (0x7) alloys, while NdCo₇C_δ phase with TbCu₇-type structure is observed in Nd₁₆Co₇₆C₈ alloy. The lattice parameter c of the Nd₂Co₁₄(B,C) phase decreases with increasing the carbon content. A limit volume of the unit cell to form the Nd₂Fe₁₄B-type structure is estimated to be 0.870 nm³. The spin-reorientation temperature T_SR increases with increasing the carbon content, due to an enhancement of magnetocrystalline anisotropy caused by carbon substitution for boron. After hydrogenation, the lattice expansion is observed for Nd₁₆Co₇₆B_8−xC_x (0x7) alloys. The spin-reorientation temperature of Nd₁₆Co₇₆B_8−xC_xH_y (0x7) is much lower than that of the host alloys. Some structural and magnetic properties of hypothetic Nd₂Co₁₄C and Nd₂Co₁₄CH_y compounds are estimated by extrapolation.