超热电子产生Kα辐射的参数影响

 超短超强激光与固体靶相互作用,可以产生大量的Kα特征谱线发射。这种Kα线光源在背光照相、医学成像和超快诊断等方面具有显著优势。为了寻求获得Kα线高产额的方法,利用ITS蒙卡模拟程序,对超短超强激光产生的超热电子在固体靶中产生的Kα线发射进行了模拟。系统研究了Kα线发射强度随出射角度、靶厚度和超热电子温度等参数的变化情况。研究发现在恒定的激光功率密度或超热电子温度下,存在最佳的靶厚度,使得Kα线光子产额最大,并用模拟结果对已有实验数据进行了解释。     

平均价电子数与掺杂铁基砷化物超导电性关系

文中提出一个计算掺杂铁基砷化物平均价电子数的方法,研究了掺杂铁基砷化物平均价电子数Zv 和转变温度Tc之间的关系,发现他们之间有一定的规律性,由此,提出用平均价电子数作为提高掺杂铁基砷化物超导电性的一个新依据.     

价电子均衡电负性及其应用

提出一种不同于传统方法的价电子均衡方法来计算均衡电负性,包括分子电负性、基团电负性和原子电荷. 用分子电负性对烷烃和单取代烷烃分子的第一电离能进行关联,用基团电负性对某些分子的¹H NMR谱化学位移进行关联,用原子电荷对脂肪族胺、醇和醚分子的气相碱性进行关联. 所得各回归方程均有良好的相关性. 同时还在价电子均衡方法的基础上对Sanderson方法和Bratsch方法进行了修正,用于关联上述各性能,结果表明比相应的原方法更为有效.     

火焰原子吸收光谱法测定温泉水中金属元素的含量

采用火焰原子吸收光谱法测定了奇村、顿村温泉水中9种金属元素Ca、Mg、Fe、Cu、Zn、Pb、Mn、Cr、Cd的含量,研究了测定不同元素的仪器最佳工作条件、方法的准确性和精密度。结果表明,该方法的加标回收率为98.10%—104.29%,相对标准偏差（n=9）为0.056%—3.32%,检出限为0.0015—0.1571mg/L。测定方法简单易行,方便准确。     

Exotic electronic states in the world of flat bands:From theory to material

It has long been noticed that special lattices contain single-electron flat bands(FB) without any dispersion. Since the kinetic energy of electrons is quenched in the FB, this highly degenerate energy level becomes an ideal platform to achieve strongly correlated electronic states, such as magnetism, superconductivity, and Wigner crystal. Recently, the FB has attracted increasing interest because of the possibility to go beyond the conventional symmetry-breaking phases towards topologically ordered phases, such as lattice versions of fractional quantum Hall states. This article reviews different aspects of FBs in a nutshell. Starting from the standard band theory, we aim to bridge the frontier of FBs with the textbook solidstate physics. Then, based on concrete examples, we show the common origin of FBs in terms of destructive interference,and discuss various many-body phases associated with such a singular band structure. In the end, we demonstrate real FBs in quantum frustrated materials and organometallic frameworks.     

Evolution of lone pair of excess electrons inside molecular cages with the deformation of the cage in e2@C60F60 systems

For unusual e(2)@C(60)F(60)(I(h), D(6h), and D(5d)) cage structures with two excess electrons, it is reported that not only the lone pair in singlet state but also two single excess electrons in triplet state can be encapsulated inside the C(60)F(60) cages to form single molecular solvated dielectrons. The interesting relationship between the shape of the cage and the spin state of the system has revealed that ground states are singlet state for spherical shaped e(2)@C(60)F(60)(I(h)) and triplet states for short capsular shaped e(2)@C(60)F(60)(D(6h)) and long capsular shaped e(2)@C(60)F(60)(D(5d)), which shows a spin evolution from the singlet to triplet state with the deformation of the cage from spherical to capsular shape. For these excess electron systems, the three ground state structures have large vertical electron detachment energies (VDEs (I) of 1.720-2.283 eV and VDEs (II) of 3.959-5.288 eV), which shows their stabilities and suggests that the large C(60)F(60) cage is the efficient container of excess electrons.     

真空硅热还原氧化锌的热力学分析

通过热力学计算并分析了真空硅热法还原氧化锌反应的吉布斯自由能. 结果表明, 在1100-1500 K温度范围内硅热还原氧化锌具有热力学上的可行性, 但是生成的SiO₂与反应物ZnO反应生成炉渣2ZnO·SiO₂, 导致约50% (w)的ZnO不能被还原. 如果加入CaO与SiO₂造渣, 就能抑制2ZnO·SiO₂的生成, 保证ZnO完全被还原成金属锌. 热力学计算表明, 造渣反应和真空工艺都可以降低还原反应的吉布斯自由能. 实验结果表明, 热镀锌灰中分离出的ZnO在温度为1448 K、真空度为20 Pa、反应时间为2 h的条件下通过硅热还原可得到具有良好结晶形貌的金属锌, 还原率为92.81%. 经X射线衍射(XRD)分析, 反应后的残渣主要成分为2CaO·SiO₂.     

Study of the performance of a thermoelectric generator transformation of the thermal energy conveyed by a heat transfer fluid into electrical energy

A mathematical model to predict the maximum energy conversion efficiency of the thermoelectric generator is developed to improve the performance and maximize the energy conversion efficiency of the thermoelectric power generator. The studied device corresponds to an original configuration of thermoelectric modules mounted on the peripheral surfaces of two channels, one of the channels is crossed by hot fluid and the other by a cold fluid. First, the effect of the flow rate was studied to choose the flow rate adapted to our study for three different configurations of the thermopile, the co-current configuration, the counter-current configuration, and the sandwich configuration. Then a comparison was made to choose the best configuration between these three studied configurations by addressing their thermoelectric performances. The results revealed that the sandwich configuration is much better than the co-current and counter-current configurations and reduces the surface area occupied by the TEG by half while generating more power than a solar panel.     

Double counting in LDA + DMFT—The example of NiO

An intrinsic issue of the LDA + DMFT approach is the so called double counting of interaction terms. How to choose the double-counting potential in a manner that is both physically sound and consistent is unknown. We have conducted an extensive study of the charge-transfer system NiO in the LDA + DMFT framework using quantum Monte Carlo and exact diagonalization as impurity solvers. By explicitly treating the double-counting correction as an adjustable parameter we systematically investigated the effects of different choices for the double counting on the spectral function. Different methods for fixing the double counting can drive the result from Mott insulating to almost metallic. We propose a reasonable scheme for the determination of double-counting corrections for insulating systems.     

Exact results relating spin–orbit interactions in two-dimensional strongly correlated systems

A 2D square, two-bands, strongly correlated and non-integrable system is analysed exactly in the presence of many-body spin–orbit interactions via the method of Positive Semidefinite Operators. The deduced exact ground states in the high concentration limit are strongly entangled, and given by the spin–orbit coupling are ferromagnetic and present an enhanced carrier mobility, which substantially differs for different spin projections. The described state emerges in a restricted parameter space region, which however is clearly accessible experimentally. The exact solutions are provided via the solution of a matching system of equations containing 74 coupled, non-linear and complex algebraic equations. In our knowledge, other exact results for 2D interacting systems with spin–orbit interactions are not present in the literature.