HOCl分子高激发振动态的动力学势研究

通过研究HOCl分子高激发振动态的动力学势, 明确了该体系的动力学特点. 研究表明, 在O-Cl伸缩模式和H-O-Cl弯曲模式间存在2:1 Fermi共振的动力学模型下, H-O伸缩振动模式对于上述两种振动模式的动力学势有显著影响, 且这种影响随Polyad数呈现有规律的变化. 作为定量研究, 还研究了Polyad数为24时该分子体系的动力学势与各能级的相空间轨迹. 分析表明, 相空间轨迹与动力学势中的动力学不动点有很好的对应关系. 此外, 将该Polyad数下的动力学势中的能级按照相空间轨迹的作用量积分进行分类, 明确了这些能级所处的量子环境.     

氮氢共掺杂金刚石中氢的典型红外特征峰的表征

所有天然Ia型金刚石红外光谱中都存在3107 cm-1特征峰,而在金属触媒直接合成的金刚石红外光谱中没有检测出3107 cm-1特征峰.本文在6.3 GPa,1500?C条件下,通过Fe70Ni30触媒中添加P3N5直接合成出具有3107 cm-1特征峰的氮氢共掺杂的金刚石.红外光谱分析表明,合成的金刚石中氢有两种存在形式:一种对应着乙烯基团C=CH2中C—H键的伸缩振动(3107 cm-1)和弯曲振动(1450 cm-1)的吸收峰,另一种对应着sp3杂化C—H键的对称伸缩振动(2850 cm-1)和反对称伸缩振动(2920 cm-1)的吸收峰.通过分析发现,3107 cm-1吸收峰与金刚石中聚集态的氮原子有关,当金刚石中没有聚集态的氮元素时,即使氮含量高也不会出现3107 cm-1峰;并且2850和2920 cm-1附近的吸收峰比3107 cm-1附近的吸收峰更为普遍存在.这说明sp3杂化C—H键比乙烯基团的C—H键更广泛存在于金刚石中,从两者的峰值看,天然金刚石中的氢杂质主要以乙烯基团C=CH2存在.3107 cm-1吸收峰与聚集态的氮原子的这种存在关系为天然金刚石形成机制的研究提供了一种新思路,同时较低的合成条件也可能为氢与其他元素共掺杂合成具有n型半导体特性的金刚石提供一个较理想的合成环境.     

Synergistic influences of titanium,boron, and oxygen on large-size single-crystal diamond growth at high pressure and high temperature

The synergistic influences of boron, oxygen, and titanium on growing large single-crystal diamonds are studied using different concentrations of B₂O₃ in a solvent-carbon system under 5.5 GPa-5.7 GPa and 1300 ℃-1500 ℃. It is found that the boron atoms are difficult to enter into the crystal when boron and oxygen impurities are doped using B₂O₃ without the addition of Ti atoms. However, high boron content is achieved in the doped diamonds that were synthesized with the addition of Ti. Additionally, boron-oxygen complexes are found on the surface of the crystal, and oxygen-related impurities appear in the crystal interior when Ti atoms are added into the FeNi-C system. The results show that the introduction of Ti atoms into the synthesis cavity can effectively control the number of boron atoms and the number of oxygen atoms in the crystal. This has important scientific significance not only for understanding the synergistic influence of boron, oxygen, and titanium atoms on the growth of diamond in the earth, but also for preparing the high-concentration boron or oxygen containing semiconductor diamond technologies.     

高压熔渗生长法制备金刚石聚晶中碳的转化机制研究

在6 GPa和1500 ℃的压力和温度范围内, 利用高压熔渗生长法制备了纯金刚石聚晶, 深入研究了高温高压下金刚石聚晶生长过程中碳的转化机制. 利用光学显微镜、X-射线衍射、场发射扫描电子显微镜检测, 发现在熔渗过程中金刚石层出现了石墨化现象, 在烧结过程中金刚石颗粒表面形貌发生了变化. 根据实验现象分析, 在制备过程中存在三种碳的转化机制: 1)金属熔渗阶段金刚石颗粒表面石墨化产生石墨; 2)产生的石墨在烧结阶段很快转变为填充空隙的金刚石碳; 3)金刚石直接溶解在金属溶液中, 以金刚石形式在颗粒间析出, 填充空隙. 本文研究碳的转化机制为在高温高压金属溶剂法合成金刚石的条件下(6 GPa和1500 ℃的压力和温度范围内)工业批量化制备无添加剂、无空隙的纯金刚石聚晶提供了重要的理论指导.     

Global dynamical analysis of vibrational manifolds of HOCl and HOBr under anharmonicity and Fermi resonance:the dynamical potential approach

The vibrational dynamics of HOCl and HOBr between bending and OCl/OBr stretching coordinates with anharmonicity and Fermi coupling is studied with the classical dynamical potential approach. The quantal vibrational dynamics is mostly mapped out by the classical nonlinear variables such as fixed points, except for the state energies, which are quantized. This approach is global in the sense that the focus is on a set of levels instead of individual ones. The dynamics of HOBr is demonstrated to be less complicated. The localized modes along the OCl/OBr stretching coordinates are also shown to have O-Br bonds more prone to dissociation.     

Design of electron wave filters in monolayer graphene with velocity modulations

We compare the transport properties of electrons in monolayer graphene by modulating the Fermi velocity inside the barrier. A critical transmission angle is found only when the Fermi velocity in the barriers is larger than the one outside the barriers. It is shown that the transmission exhibits periodicity with the incident angle below the critical transmission angle, and attenuates exponentially in the opposite situation. For both situations, peak splitting occurs in the transmission as the number of the velocity barriers increases, and the characteristics of the transmission suggest an interesting application of an excellent band-pass filter. The dependence of the conductance on the Fermi energy through an identical velocity- modulation structure differs wildly with different Fermi velocities of the barrier. The counterpart of the peak splitting is the sharp oscillations in the conductance profile. Furthermore, some oscillations for the multiple barriers are so sharp that the structure may be used as an excellent sensor.     

甲基紫分子拉曼激发虚态的研究

从拉曼峰强入手,求得了甲基紫分子的“时间分辨键极化率”,并与第一原理计算的基态电子密度做对比,讨论了该分子的激发拉曼虚态的性质.研究结果表明,该分子的拉曼激发虚态中电子向分子外围以及两环之间的键流动,并且拉曼弛豫后的键极化率分布与基态电子的密度分布相似.通过研究键极化率的弛豫过程,发现连接两环的键上的键极化率弛豫时间较其他键大.这些结果说明了甲基紫这类双环分子拉曼激发虚态的性质,这对于研究拉曼散射的中间态具有一定意义. 关键词： 拉曼峰强 时间分辨键极化率 弛豫特征时间     

朗之万方程及其在蛋白质折叠动力学中的应用

研究了朗之万方程的动力学性质,并用它模拟了蛋白质分子的折叠过程.首先在相空间中对朗之万方程做连续映射,发现做布朗运动的粒子在位置坐标上存在明显的概率分布,这表明蛋白质折叠过程中分子空间构型是非遍历的.此外,本文还通过数值模拟得到了去折叠态蛋白质的紧密度指标,并验证了它与实验结果以及其他理论方法的一致性.本文还提出了一种利用重整化方法研究熔球体状态蛋白质的理论模型,并提供了考虑疏水基影响的蛋白质折叠过程的模拟思路. 关键词： 朗之万方程 蛋白质折叠非遍历性 紧密度指标 重整化     

基于复杂性测度的高温气冷堆模拟机运行模式识别及诊断研究

本文通过对高温气冷堆模拟机在运行过程中的12组状态参数进行分析,研究了反应堆在正常运行状态、 余热排出系统空气侧温度上升和一回路突然泄漏三种条件下系统的复杂度和稳健性等指标的变化. 研究表明,在条件发生改变时,高温气冷堆模拟机系统的复杂度有非常明显的变化,且不同条件下, 对于系统复杂性影响显著的参数也不相同.此外,反应堆模拟机中各系统间耦合计算与相互反馈机理的作用, 在系统的稳健度上也有很明显的体现.这些成果表明,复杂性分析方法在系统状态监测和 危机预警领域可以发挥重要的作用.     

包覆燃料颗粒碳化硅层的Raman光谱研究

本文研究了球床高温气冷堆燃料元件中包覆颗粒碳化硅层的Raman光谱. 通过分析不同制备条件下的碳化硅层断面的Raman光谱的峰位、半高全宽与强度, 明确了包覆颗粒中碳化硅层的晶相特征、密度变化和剩余应力等物性.通过分析不同密度碳化硅层一级Raman峰的同步、异步二维相关谱, 发现其LO模较TO模对于密度变化的响应更敏感. 这些结论为研究球床高温气冷堆燃料元件包覆颗粒中碳化硅层的结构及其物性有指导意义.