氢化铁的自旋极化效应及势能函数

B3LYP/6-311++g**水平上预测了FeH2及FeH稳定构型讨论了其自旋极化效应,并与实验结果进行了比较.结果表明其基态分别为FeH2(5A1)和FeH(4?),自旋态对构型和物理性质均有显著影响.FeH2具有C2v对称性.势能与核间距的关系用4参数Murrell-Sorbie函数进行拟合得到其分析势能函数.由此推导出力常数和光谱数据,并由多体项展式理论导出了基态FeH2分子的分析势能函数.用这个分析势能函数分析表明:H+FeH生成FeH2(C2v)分子通道存在一个4.68 eV深的势阱,易生成H—Fe—H络合物分子.反应Fe+H2→HFeH,?H=-0.08305 eV,是放热反应.     

三维传输子量子比特的退相干参数表征

超导量子比特的退相干时间是决定超导量子计算能否实现的重要指标之一. 文章以三维传输子量子比特(3D transmon)为研究对象, 在氧化硅衬底上制备了三维传输子量子比特, 并在超低温下(10 mK), 采用拉比振荡(Rabi oscillation)、能量弛豫(energy relaxation)、 拉姆齐条纹(Ramsey fringe)、自旋回波(spin echo)的方法, 对其进行了详细的退相干时间常数表征. 结果显示该量子比特的退相干时间在几百纳秒. 根据几种退相干时间的关系进行计算, 可以看出, 低频噪声目前不是影响量子比特退相干的最主要因素, 而氧化硅中的缺陷可能是样品退相干时间的主要瓶颈. 关键词： 三维传输子量子比特 拉比振荡 拉姆齐条纹 自旋回波     

F原子吸附TiO_2:Mn(001)稀磁半导体薄膜电子结构和磁性的第一性原理计算

利用第一性原理方法计算Mn离子掺杂纯净TiO2(001)和F原子吸附的TiO2(001)薄膜的形成能、态密度和磁矩.F原子吸附明显降低TiO2∶Mn薄膜体系的形成能.F原子的吸附导致Mn离子的磁矩减小,而表面O原子的磁矩增大.表面O原子的磁矩主要来源于O原子p x和p y轨道的自旋极化,研究表明表面吸附F原子更有利于Mn离子的掺杂,在一定程度上有利于获得结构稳定的铁磁态半金属特性的TiO2∶Mn薄膜.     

含氮-空位缺陷锯齿状石墨烯纳米条带中负微分电阻和自旋过滤效应

采用第一性原理和非平衡格林函数方法,系统研究了含氮空位缺陷锯齿状石墨烯纳米条带的自旋极化输运特性．理论计算结果表明边界非对称的这类石墨纳米条带的基态具有铁磁性,由其构建的分子结中负微分电阻效应具有鲁棒性,是电极局域的态密度及依赖偏压的散射区-电极耦合作用结果．此外,在特定偏压区域还观察到几乎完美的自旋过滤效应．     

学会思维调控

同学们知道,解决一个数学问题的过程,从本质上来看,就是不断进行思维调控的过程.思维调控的目的,在于能够使问题由隐约变得清晰,由复杂变得简单.一般地,解题中思维调控究竟调控什么？本文试图通过具体的实例加以总结,仅供同学们参考.一、调控问题结构对相当数量的数学问题,若要解决它们,其关键在于调控问题的内在结构.只要把隐含在问题之中的结构捣腾清楚了,问题也就自然解决了.请看以下两例：     

Description of the shape evolution in the yrast states of ~（186）Pt

^186Pt was tested in the framework of IBM-1 and the X（3） model. The results show that ^186Pt is located close to the shape phase transition point, but the B（E2） values little agree with the X（3） model. The shape evolution in the yrast states of186Pt is also discussed in detail. TRS calculation exhibits a flat bottomed potential at low spin states, but a relatively deep minimum at high spin states. It suggests that a shape evolution from vibrational mode to rotational mode happens in ^186Pt. The result is in agreement with the E-GOS calculation.     

Pairing symmetry in layered BiS2 compounds driven by electron-electron correlation

We investigate the pairing symmetry of layered BiS2 compomlds by assuming that electron-electron correlation is still important so that the pairing is rather short range. We lind that the extended .s-wave pairing symmetry always wins over d-wave when the pairing is confined between two short range sites up to next nearest neighbors. The pairing strength is peaked around the doping level ：r = 0.5. which is consistent with experimental observation. The extended s-wave pairing symmetry is very robust against spin orbital coupling because it is mainly determined by the structure of Fermi surfaces, Moreover. the extended s-wave pafiring can be distinguished from conventional swave pairing by measuring and comparing superconducting gaps of different Fermi surfaces.     

Experimental observations of ferroelectricity in double pyrochlore Dy2Ru2O7

Double pyrochlore Dy2Ru207 is synthesized and its magnetism and ferroelectricity below the Ru4＋ spin ordering temperature （NI00 K） are investigated. The ferroelectric transition appears at -18 K, much higher than the Dy3＋ spin ordering point at -1.8 K and lower than the Ru4＋ spin ordering point at -100 K. The measured electric polarization at ,-2 K is as big as 145℃/m2 in the polycrystalline samples. It is argued that the ferroelectricity is possibly ascribed to the electric dipole ordering arising from the collective monopole excitations in the Dy3＋ tetrahedrons in prior to the Dy3＋ spin ordering into spin-ice like state below -1.8 K.     

坑口电厂低碳经济发展系统动力学仿真研究

通过分析坑口电厂低碳经济系统的复杂结构特征和动态反馈机制,建立了坑口电厂低碳经济系统动力学模型,描述系统内部各要素之间的相互关系,并以平煤集团坑口电厂为例,对不同发展方案下的坑口电厂低碳经济系统进行仿真模拟.结果表明:科技投资、环保投资、能源利用率、能源消费结构等因素是影响坑口电厂低碳经济发展的关键因素;可以通过优化能源消费结构,提高煤矸石消耗比例;增加科技投资和环保投资,提高能源利用和转换效率,降低污染物和二氧化碳排放量,从而达到高效率、低能耗、低排放的低碳经济发展模式.