几何结构对Na8团簇熔化过程的影响

运用距离相关紧密结合的分子动力学模型,对金属原子团簇Na8的两种不同的异构体进行了数值模拟.根据零温下基态结构中不同原子到质心的不同距离,把Na8的两种异构体分为多个子系统.分别提取各个子系统在不同温度下的围绕质心的径向分布、无单位键长涨落、平均位移、扩散系数,发现尽管两个异构体的基态能量很接近,但他们的稳定性、熔化过程的热力学性质等有着很大的差别,这也反映了它们在几何结构上的差别.     

几何结构对Na8团簇熔化过程的影响

运用距离相关紧密结合的分子动力学模型。对金属原子团簇Na8的两种不同的异构体进行了数值模拟．根据零温下基态结构中不同原子到质心的不同距离，把Na8的两种异构体分为多个子系统．分别提取各个子系统在不同温度下的围绕质心的径向分布、无单位键长涨落、平均位移、扩散系数。发现尽管两个异构体的基态能量很接近。但他们的稳定性、熔化过程的热力学性质等有着很大的差别，这也反映了它们在几何结构上的差别．     

Paul阱中共面两离子系统的能量本征态

通过对Paul阱中共面两离子体系的研究，考虑共面两离子在Paul阱中库仑关联，得到了两离子系统Schrdinger方程的精确解；椐方程的精确解，分析了质心能级简并情况，计算了两离子的平衡距离和低能级的几个态函数，设计程序作出了质心径向概率分布图. 关键词： Paul阱 两离子 共面 量子逻辑操作     

基态α-环己二酮最优解离路径中环状异构体的红外光谱分析

在CCSD(T)//B3LYP/6-311++G(d,p)理论水平上研究了基态α-环己二酮（α-CHD）到环戊酮（c-C5H8O）和一氧化碳（CO）的光解离反应势能面（PES）,并计算了沿反应路径各环状异构体的红外光谱。从过渡态的相对能量、高能势垒的数目两个方面,并结合红外光谱研究结果确定了α-CHD→c-C5H8O+CO的最优光解离路径。对其势能面上的环状异构体进行了红外光谱分析,给出各异构体的振动频率、振动强度和主要的振动模式,与实验结果吻合较好。计算结果为基态α-CHD提出了一条新的最优解离路径,同时丰富了其环状异构体的光谱信息。     

几何构型不同的Na团簇碰撞动力学研究

采用距离相关紧密束缚的分子动力学模型,在不同碰撞能量以及不同的碰撞参数下,研究了两种构型的Na6(2D),Na6(3D)与Na8团簇间的碰撞.讨论了反应机制的变化,即全融合、深度非弹、非弹性碰撞过程.结果表明:构型不同的团簇与相同的靶碰撞显示了不同的特征.低能时Na6(3D)易融合;DIC反应时,易于形成大的团簇 关键词： Na团簇 原子团簇碰撞 紧束缚模型     

Cs(8D,9D)+Na(3S)碰撞激发转移过程

此文报道异核Cs(8D,9D)+Na(3S)→Cs(6P)+Na(3P)的碰撞能量转移过程.两步激发Cs原子到9D3/2(8D3/2)态.应用双调制技术探测Na(3PJ)原子发射的荧光,基态Na原子密度用光学吸收方法测量.得到了REP率系数,讨论了其它过程对率系数的影响.     

In_nNa_m和In_nNa_m~+(n+m≤5;m,n≠0)团簇结构和性质的研究

采用密度泛函理论中的B3LYP方法,对In_nNa_m和In_nNa_m~+(n+m≤5;m,n≠0)混合团簇的所有可能构型进行了优化,并作了频率计算.结果表明:较大团簇大多是由较小团簇生长而来的,In_3Na_2团簇有较为丰富的异构体,绝大多数阳离子团簇的稳定结构与其中性稳定结构是相似的;中性团簇基态结构的平均结合能和能隙随Na原子个数变化的趋势基本一致;InNa_3和In_3Na_2的垂直电离能和绝热电离能的差别较大;团簇中的Na原子容易失去电子,而In原子倾向于得到电子.     

极性晶体界面附近激子的性质

本文利用么正变换方法计算了极性晶体界面附近激子的基态能量,得到了激子基态能量及倒半径随激子质心距界面距离变化的曲线。发现当晶体在真空中时,表面会出现死层,晶体与金属相接触时,界面附近会出现相变。     

密度泛函方法研究气相胞嘧啶的互变异构化

分别采用7种基组、3种理论方法对胞嘧啶异构体Cyt1的结构进行优化,通过与Cyt1的实验结果进行比较,选取了适合研究胞嘧啶分子的B3LYP/6311+G方法.用该方法对胞嘧啶分子的8种异构体构型进行了充分优化,研究了其中能量较低的6种胞嘧啶异构体的互变异构化过程.对于得到的所有优化构型都进行了频率分析.对于基态构型,所有的频率都是正的;对于过渡态构型,只有一个虚频.同时,做了详尽的内禀反应坐标计算,以保证所得到的过渡态连接相应的始末异构体.所有给出的能量都已做了零点能校正.理论研究结果可以对已有的实验结果给予合理解释.     

Na6团簇2D和3D结构的竞争

在距离相关紧密结合分子动力学模型的基础上，对Ｎａ６两个最低能量异构体（一个具有Ｃ５ｖ对称性，是３Ｄ结构，另一个具有Ｄ３ｈ对称性，是２Ｄ结构）的结构性质进行了研究。通过求解Ｈｅｓｉａｎ矩阵和对距离相关紧密结合分子动力学轨道所作的速度自关联函数的福里叶变换分析，得到了这些钠原子微团簇的振动频率。尽管这两种结构的能量很接近，但它们表现出完全不同的振动性质，这反映了其几何结构的差别。     

有限温度下Na4团簇的异构化

在紧密结合分子动力学模型基础上,对Ｎａ４的两种异构体Ｄ２ｈ和Ｃ２Ｖ和结构性质随温度的进行了系统性研究。发现在低温时,这两划构体具有明显有不同;在较高温度时,能够发现Ｃ２Ｖ和Ｄ２ｈ两种异构体之间的转变;在更高温度时,这两种异构体Ｃ２ｖ和Ｄ２ｈ都处于液态。     

Codoping Na+ to modulate the spectroscopy and photoluminescence properties of Yb3+ in CaF2 laser crystal

Three kinds of Yb3+ - and Na+-codoped CaF2 laser crystal with different Na:Yb ratios of 0, 1.5, and 10 are grown by the temperature gradient technique. Room-temperature absorption, photoluminescence spectra, and fluorescence lifetimes belonging to the transitions between ground state 2F7/2 and excited state 2F5/2 of Yb3+ ions in the three crystals are measured to study the effect of Na+. Experimental results show that codoping Na+ ions in different Na:Yb ratios can modulate the spectroscopy and photoluminescence properties of Yb3+ ions in a CaF2 lattice in a large scope.     

A study of the dynamic equilibrium between symmetrical and distorted 1,2,3-trimethylcyclohexane radical cations

Radical cations of the 1,2,3-trimethylcyclohexane isomers stabilized in various γ-irradiated solute/halocarbon matrices have been investigated by means of ESR in the temperature range 4–77K. At 4 K the ESR spectra are dominated by contributions from an asymmetrically distorted structure with the unpaired electron localized to the C1-C2 bond. On increasing the temperature a reversible change occurs in the ESR line-shape of the cations of the two symmetrical isomers. Using a two-site jump model to reproduce the temperature dependent line-shape, the phenomenon is explained in terms of an interconversion between two such distorted structures, each being the mirror image of the other. The Arrhenius plot associated with the process is markedly nonlinear towards the low temperature region. The experimental data are also modelled by postulating that another (different) electronic ground state, having higher symmetry, becomes populated with the increase of temperature. In this way, the spectral changes can be simulated using a three-site jump model which couple the thermally activated two-site jump process (E _a ca. 0.137 kcal/mol) with a dynamical equilibrium between the asymmetrical ground state and a symmetrical structure 0.058 kcal/mol higher in energy. The energy barrier to pass from the distorted to the symmetrical structure was evaluated to be 0.085 kcal/mol.     

锗团簇Ge65, Ge70, Ge75的稳定结构及其电子结构性质

将两种全局结构搜索方法(压缩液态法、遗传算法)与锗的紧束缚势模 型相互结合, 对Ge₆₅, Ge₇₀, Ge₇₅的稳定结构进行了大规模的搜寻,提 出能量较低的可能结构, 然后进一步利用第一性原理方法对这些低能结构进行精确 的优化计算, 确定出了这三种尺寸团簇的基态结构. 发现这三种团簇各具有两种稳定的并且能量相近的异构体: 类球形和类椭球形, 这与实验上报道的大尺寸团簇Ge_n (65 ≤ n ≤ 80) 的结构特征相符合. 简要地分析了这三种团簇基态结构的电子性质. 关键词： 锗团簇 紧束缚势 遗传算法 压缩液态法     

(XB2)2(X=Al, Be, Na, Mg)团簇的密度泛函研究

用密度泛函理论(DFT)的杂化密度泛函B3LYP方法在6-31G*基组水平上对(XB2)2(X=Al,Be,Na,Mg)团簇各种可能的构型进行几何结构优化,预测了各团簇的最稳定结构.并对最稳定结构的电子结构、振动特性、成键特性和电荷特性等进行了理论研究.结果表明,团簇的几何结构大多是平面结构,通常是B-B键和B-X键共存,较少出现X-X键.团簇的稳定结构中通常是几个呈负电性的B原子形成一个负电中心,而其他B原子和X原子处在端位,且显正电性.     

Correlations between vapor-phase Na/K/As adsorption capacities of kaolinite and temperature-dependent derivation of its Al-containing groups

Kaolinite is a commonly used additive, which has been proven to be capable of in-furnace capturing the vapor-phase Na, K, and As, so as to alleviate the fouling and slagging on the heat-exchange surface, the poisoning of selective catalytic reduction (SCR) catalyst, and to reduce related environmental pollution. Considering that temperature-dependent derivation of kaolinites significantly influence the collaborative removal of these vapors, the present study quantified the Na/K/As adsorption capacity of kaolinites using a self-designed device over a wide temperature range to explore the temperature window for high adsorption efficiency. By analyzing Al-coordination of kaolinites before and after adsorption, fixation pathway of Na/K/As vapor was revealed. Effect analysis of single adsorbed atom combined with adsorption energy calculation based on density functional theory (DFT) was performed to demonstrate the difference of adsorption sites for Na/K/As vapors. The results showed that kaolinites had high Na/K/As adsorption capacity at 1073 K–1173 K, 723 K–1273 K, and 1173 K, respectively. When the temperature was between 723 K and 1173 K, the primary hexa-coordinated ^[VI]Al of kaolinites transformed into penta-coordinated ^[V]Al/tetra-coordinated ^[IV]Al. The newly formed ^[IV]Al atoms bonded with Na/K/As atoms. Specifically, both of center sites and bridge sites of ^[IV]Al-O rings can offer position for the fixation of Na and K atoms, and Na atoms were prone to be fixed at the former sites, while K atoms were easy to locate at the latter. In contrast, almost only the center sites of ^[IV]Al-O rings contributed to As adsorption. Thus, with the segmented injection of kaolinites at different temperature within 723 K–1273 K, development of two kinds of modified kaolinites with more center sites or bridge sites of ^[IV]Al–O rings were recommended to avoid competitive adsorption and realize collaborative removal of Na/K/As vapors.     

Theoretical Study on the Stable Structures and Aromaticities for Pnictogen Dianionic Sb42-, Bi42-, and (SbBi)22- Clusters

运用密度泛函方法(B3LYP)和后Hartree-Fock (post-HF：MP2、CCSD(T)),对三个新的磷属二价阴离子团簇Sb42-、Bi42-和(SbBi)22-的几个可能的同分异构体进行结构优化、振动频率和原子化能的理论计算．计算结果表明Sb42-和Bi42-团簇有三种稳定的结构：正方形(D4h)、屋顶型(roof,C2v-1)和C2v-2结构,其中正方形结构是基态．由异原子组成的(SbBi)22-团簇也有三种稳定结构：菱形(D4h)、屋顶型(roof,C1)和C2v结构,其中菱形结构是基态．计算显示Sb42-、Bi42-和(SbBi)22-团簇的所有屋顶型(roof)结构的核独立化学位移(NICS)全部为负值,从而说明这些屋顶型结构拥有芳香性;平面环结构(正方形或菱形)的核独立化学位移值全部为正值,说明这三种平面环结构具有反芳香性．用分子轨道分析对这两类屋顶型和平面环结构的芳香性和反芳香性作了解释和讨论．     

Damping performance of two simple oscillators coupled by a visco-elastic connection

A simple dynamic system composed of two linear oscillators is employed to analyze the passive control performance that can be achieved through a visco-elastic damper connecting two adjacent free-standing structures. By extension, the model may also describe the energy dissipation which can be obtained by an internal coupling between two quasi-independent sub-systems composing a single complex structure. Two alternatives are evaluated for the linear coupling by considering either the serial or the parallel spring–dashpot arrangement known as the Kelvin–Voigt and the Maxwell damper model, which may synthetically reproduce the constitutive behavior of different industrial devices. The complex eigenvalues of the coupled system are parametrically analyzed to determine the potential benefits realized by different combinations of the coupling stiffness and damping coefficient. A design strategy to assess these parameters is outlined, driven by the relevant observation that a perfect tuning of the natural frequencies always corresponds, in the parameter space, to the maximum modal damping for one of the resonant modes, independent of the damper model. The effectiveness of the proposed strategy is discussed for different classes of the controlled system, depending on the mass and stiffness ratio of the component oscillators. As a major result, different design parameter charts for the two damper models are carried out and compared to each other. Performance indexes are introduced to quantitatively evaluate the passive control performance with respect to the mitigation of the system forced response under harmonic and seismic ground excitation. The analyses confirm the validity of the design strategy for a well-balanced mitigation of the displacement and acceleration response in both the oscillators.     

胭脂红和苋菜红分子结构与光谱性质的对比研究

应用英国Edinburgh FLS920P稳态-瞬态荧光光谱仪,对互为同分异构体的胭脂红、苋菜红分子的吸收光谱和荧光光谱实验检测,得到二者的光谱特性参数,并进行对比。分别采用密度泛函理论（DFT）和含时密度泛函理论（TD-DFT）对这两种分子的基态和激发态结构进行优化,将所得基态分子构型进行频率计算,结果显示均无虚频存在,进而比较两分子构型在不同能态下的差异。在此基础上,应用TD-DFT并结合极化连续介质模型（PCM）在6-311++G(d, p)水平上分别计算二者的吸收光谱和荧光光谱,对两种分子的发光机制、荧光光谱特性差异与分子结构的关系进行了分析。结果表明,两种分子的基态结构均为非平面,它们中的两个萘环不共面,存在一定的夹角;苋菜红含有分子内氢键,且氢键所在萘环的平面性要优于胭脂红分子对应的萘环部分;激发态时二者各自的两个萘环均共平面。量子化学计算得到的光谱理论值与实验结果较为吻合,说明优化所得胭脂红与苋菜红的分子构型基本合理。与苋菜红相比,胭脂红右侧萘环结构的平面性稍差,分子从激发态跃迁回到基态经历了更多的振动和转动,损耗了更多的能量,导致用来产生荧光光子的能量减少,因此,胭脂红的荧光发射波长更长。本文首次得到胭脂红、苋菜红分子基态与激发态下的分子结构信息,并找出二者光谱特性差异的原因,结果可为研究同分异构体分子的光谱特性与分子结构的关系提供参考。