Ce掺杂锐钛矿型TiO_2密度的泛函理论应用

采用基于密度泛函理论(DFT)框架下的第一性原理平面波赝势(PWPP)方法,模拟计算了纯的TiO2和Ce掺杂锐钛矿TiO2的能带结构、态密度及光学性质,分析了Ce掺杂对锐钛矿TiO2的晶体结构、能隙、态密度和光吸收系数的影响.结果表明:Ce掺杂锐钛矿TiO2晶体后,Ce的4 f轨道进入导带使导带底向低能端移动,禁带宽度变小,吸收带红移,可见光区具有较大的光吸收系数,从而有助于提高TiO2的光催化活性,理论与实验基本吻合.     

近藤化合物Ce2CuxNi1-xGe6的磁性和晶场模拟

通过对磁化率的模拟,研究了晶场效应对Ce2CuxNi1-xGe6磁性的影响,得到了该系列化合物的分裂能和相应波函数.计算表明,Ce3 六重基态在晶场作用下分裂为混合的双基态,其晶场分裂能随X的增大而变大.Cu含量的增加引起了更加复杂的f电子和传导电子的杂化,低温区域的电子—磁子近藤散射变得更加强烈.     

Ce_(1-x)Y_xPt_2Si_2(x=0.2,0.55,0.9)的晶场模拟

采用点电荷晶场理论模型,通过对Ce1-xYxPt2Si2(x=0.2,0.55,0.9)磁化率倒数—温度曲线的模拟,得到了其晶场分裂能和相应波函数,计算表明:晶场分裂能随x的增大而减小,晶场作用使得Ce3+六重简并基态分裂得到混合的双基态.     

Photoelectron spectroscopy of terpenoids and prediction of their rate constants in atmospheric oxidation reactions

The electronic structures of six mono-terpenoids and two of their oxygenated derivatives were studied by He I photoelectron spectroscopy (PES). The observed bands were interpreted on the basis of empirical arguments and theoretical calculations. The first vertical ionization potentials for β-pinene, α-terpinene, terpinolene, γ -terpinene, limonene, myrcene, citral, and terpinene-4-ol were determined to be 8.73, 7.57, 8.26, 8.30, 8.53, 8.68, 8.71, and 8.77 eV, respectively. Most of these values have not been determined by PES before. The correlations of the first vertical ionization potentials of these compounds to the natural logarithms of rate constants for their reactions with the radicals OH, NO3, and O3 were determined. The correlation coefficients for their reactions with OH, NO₃, and O₃ were 0.97, 0.91, and 0.95, respectively. This method is a powerful technique for predicting the rate constants for the atmospheric oxidation reactions of terpenoids.     

High-resolution spectroscopy of two-dimensional electron systems

Spectroscopic methods involving the sudden injection or ejection of electrons in materials are a powerful probe of electronic structure and interactions. These techniques, such as photoemission and tunnelling, yield measurements of the 'single-particle' density of states spectrum of a system. This density of states is proportional to the probability of successfully injecting or ejecting an electron in these experiments. It is equal to the number of electronic states in the system able to accept an injected electron as a function of its energy, and is among the most fundamental and directly calculable quantities in theories of highly interacting systems. However, the two-dimensional electron system (2DES), host to remarkable correlated electron states such as the fractional quantum Hall effect, has proved difficult to probe spectroscopically. Here we present an improved version of time-domain capacitance spectroscopy that allows us to measure the single-particle density of states of a 2DES with unprecedented fidelity and resolution. Using the method, we perform measurements of a cold 2DES, providing direct measurements of interesting correlated electronic effects at energies that are difficult to reach with other techniques; these effects include the single-particle exchange-enhanced spin gap, single-particle lifetimes in the quantum Hall system, and exchange splitting of Landau levels not at the Fermi surface.     

一些磷化合物的X射线光电子能谱

本文研究了一些磷化合物的X射线光电子能谱,测定了磷1s电子的结合能、磷2p电子结合能和磷KLL俄歇电子能量,首次报导了九个磷化合物的有关电子能谱值,并讨论了这些电子能谱位移与化学状态之间的对应关系.     

Biotemplated fabrication of hierarchical mesoporous CeO2 derived from diatom and its application for catalytic oxidation of CO

Hierarchically hollow nanostructures have been the focus of numerous studies due to their prominent physicochemical properties that differ significantly from bulk materials and their potential for extensive applications. We present a novel diatom-based scaffold for the synthesis of hierarchically biomorphic CeO2 with special porous structure via incorporating Ce ions into the frustule. Scanning electron microscopy, transmission electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, and nitrogen adsorption-desorption measure- ments were adopted to characterize the products. Owing to its unique hierarchical structure and periodic meso-macro scale features, the obtained CeO2 exhibits high catalytic activity in CO oxidation. This facile strategy may design a new way towards replicating desired biological structures for metal oxide catalyst in other potential applications.     

氮铝簇合物的结构与稳定性

采用密度泛函理论（DFT）中的B3LYP方法,以6－31G标准基组加一个极化函数,对（ClAlNH)10和（AlN)10簇合物分子的几何构型、电子结构和红外光谱进行了优化计算,并讨论了它们的化学键特征。研究结果表明,（ClAlNH)10和（AlN)10簇合物的基态稳定结构均具有C2h对称,不存在Al-Al和N－N键,因此Al-N键是惟一的键型。     

Electronic Structure and Electron-transport Properties of Peanut-shaped C60 Polymers with a Negative Gauss Curvature

1 Results When a C60 film was irradiated with electron-beam (EB) with an incident energy of 3 kV, a peanut-shaped C60 polymer with metallic properties was formed[1], as shown in Fig.1. To elucidate the origin of the metallic properties of the peanut-shaped polymer, we examined the valence photoelectron spectra of the polymer using in situ high-resolution photoelectron spectroscopy and found that the electronic states of the polymer came across the Fermi level (EF)[2]. Interestingly, the spectral shape i...     

反射不对称相对论平均场理论对Ce同位素链形状演化的研究

用反射不对称相对论平均场理论（Reflection Asymmetric Relativistic Mean Field,i.e.：RAS-RMF）对Ce同位素链的基态性质及形状演化进行了研究.结果表明：引入反射不对称自由度自由度,RMF理论能很好地描述Ce同位素的基态性质,计算的结合能与实验数据符合得相当好,获得的形变参数、单粒子能级、物质密度分布及位能曲线清晰地展现出偶偶核Ce同位素的形状演化.     

纤锌矿氮化物半导体中电子-声子相互作用对表面电子态的影响

采用变分法研究了半无限纤锌矿氮化物半导体中电子表面态问题. 计及电子与表面光学声子相互作用和结构异性的影响导出了系统的有效哈密顿量, 获得了电子表面态能级、电子与表面光学声子相互作用能量分别随表面势垒的变化关系. 对GaN, AlN和InN进行了数值计算.结果表明,电子与表面声子的相互作用使电子的表面能级下降, 并且纤锌矿结构的GaN和AlN中电子-声子相互作用能量较闪锌矿结构大,而对InN情况正好相反.在计算的所有材料中纤锌矿材料的电子表面能级比闪锌矿的低几百meV.电子与表面光学声子相互作用对表面电子态的影响不应被忽略.     

Low-energy acoustic plasmons at metal surfaces

Nearly two-dimensional (2D) metallic systems formed in charge inversion layers and artificial layered materials permit the existence of low-energy collective excitations, called 2D plasmons, which are not found in a three-dimensional (3D) metal. These excitations have caused considerable interest because their low energy allows them to participate in many dynamical processes involving electrons and phonons, and because they might mediate the formation of Cooper pairs in high-transition-temperature superconductors. Metals often support electronic states that are confined to the surface, forming a nearly 2D electron-density layer. However, it was argued that these systems could not support low-energy collective excitations because they would be screened out by the underlying bulk electrons. Rather, metallic surfaces should support only conventional surface plasmons-higher-energy modes that depend only on the electron density. Surface plasmons have important applications in microscopy and sub-wavelength optics, but have no relevance to the low-energy dynamics. Here we show that, in contrast to expectations, a low-energy collective excitation mode can be found on bare metal surfaces. The mode has an acoustic (linear) dispersion, different to the dependence of a 2D plasmon, and was observed on Be(0001) using angle-resolved electron energy loss spectroscopy. First-principles calculations show that it is caused by the coexistence of a partially occupied quasi-2D surface-state band with the underlying 3D bulk electron continuum and also that the non-local character of the dielectric function prevents it from being screened out by the 3D states. The acoustic plasmon reported here has a very general character and should be present on many metal surfaces. Furthermore, its acoustic dispersion allows the confinement of light on small surface areas and in a broad frequency range, which is relevant for nano-optics and photonics applications.     

Electronic States of Some Semiconductor Clusters

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Violet/blue photoluminescence from CeO_2 thin film

CeO2 is a rare-earth oxide which has a face centered cubic fluorite crystal structure. It has fine chemical stabil-ity and high dielectrics (e = 26). Its lattice constant has closely matched to silicon and the dismatch is about 0.35%. It is always investigated as insulator material in the silicon-on-insulator (SOI) structures, dielectric mate-rial and the buffer layer between the superconductor Yba2Cu3O7 and the Si substrate[1—6]. Recently, the PL of CeO2 was studied by many groups. The…     

Free-electron-like dispersion in an organic monolayer film on a metal substrate

Thin films of molecular organic semiconductors are attracting much interest for use in electronic and optoelectronic applications. The electronic properties of these materials and their interfaces are therefore worth investigating intensively, particularly the degree of electron delocalization that can be achieved. If the delocalization is appreciable, it should be accompanied by an observable electronic band dispersion. But so far only limited experimental data on the intermolecular dispersion of electronic states in molecular materials is available, and the mechanism(s) of electron delocalization in molecular materials are also not well understood. Here we report scanning tunnelling spectroscopy observations of an organic monolayer film on a silver substrate, revealing a completely delocalized two-dimensional band state that is characterized by a metal-like parabolic dispersion with an effective mass of m* = 0.47m(e), where m(e) is the bare electron mass. This dispersion is far stronger than expected for the organic film alone, and arises as a result of strong substrate-mediated coupling between the molecules within the monolayer.     

Ti^19＋离子的能量和量子亏损

利用全实加关联（FCPC）方法计算了类锂Ti^19＋离子的激发态1s2nl（l=d,f,n≤9）的非相对论的电离能;将相对论效应（电子动能的相对论修正,Darwin项,电子-电子接触项以及轨道-轨道相互作用）和质量极化效应作为微扰,计算了它们对体系能量的修正;利用有效核电荷方法计算了电子的量子电动力学（QED）效应对电离势和激发能的贡献。在用FCPC方法得到的Ti^19＋离子的激发态能量的基础上,以单通道量子亏损理论（QDT）为依据,计算了这两个Rydberg系列的量子数亏损;将得到的量子数亏损作为输入,根据Rydberg公式又实现了对任意高激发态的能量的理论预言。     

Collapse of long-range charge order tracked by time-resolved photoemission at high momenta

Intense femtosecond (10(-15)?s) light pulses can be used to transform electronic, magnetic and structural order in condensed-matter systems on timescales of electronic and atomic motion. This technique is particularly useful in the study and in the control of materials whose physical properties are governed by the interactions between multiple degrees of freedom. Time- and angle-resolved photoemission spectroscopy is in this context a direct and comprehensive, energy- and momentum-selective probe of the ultrafast processes that couple to the electronic degrees of freedom. Previously, the capability of such studies to access electron momentum space away from zero momentum was, however, restricted owing to limitations of the available probing photon energy. Here, using femtosecond extreme-ultraviolet pulses delivered by a high-harmonic-generation source, we use time- and angle-resolved photoemission spectroscopy to measure the photoinduced vaporization of a charge-ordered state in the potential excitonic insulator 1T-TiSe(2 )(refs 12, 13). By way of stroboscopic imaging of electronic band dispersions at large momentum, in the vicinity of the edge of the first Brillouin zone, we reveal that the collapse of atomic-scale periodic long-range order happens on a timescale as short as 20?femtoseconds. The surprisingly fast response of the system is assigned to screening by the transient generation of free charge carriers. Similar screening scenarios are likely to be relevant in other photoinduced solid-state transitions and may generally determine the response times. Moreover, as electron states with large momenta govern fundamental electronic properties in condensed matter systems, we anticipate that the experimental advance represented by the present study will be useful to study the ultrafast dynamics and microscopic mechanisms of electronic phenomena in a wide range of materials.     

面心立方和亚稳液相Cu的电子结构和物理性质

根据SGTE数据库的晶格稳定参数和Debye-Gruneisen模型,运用纯金属单原子(OA)理论研究了面心立方和亚稳液相Cu的原子状态、原子势能、原子动能、原子体积、体弹性模量和热膨胀系数等物理参数随温度的变化关系。研究结果表明:电子结构计算结果与采用第一原理方法所得的结果一致;单键半径,原子动能和原子势能随温度上升而增加;线热膨胀系数计算值与实验值较吻合;固液相变时,Liquid-Cu的自由电子和共价电子均向非键电子转移,共价d电子向共价s电子转移,电子结构的转变降低液相的导电性,削弱液相原子配位的方向性,引起原子单键半径和体积增大。     

过渡金属硼化物RuB和TcB的晶体结构、弹性性质和电子结构第一性原理计算研究

采用基于密度泛函理论的第一性原理计算方法研究了RuB和TcB的晶体结构、弹性和电子结构等性质.对于每种化合物,分别考虑了两种可能的结构(WC、ZnS).研究结果表明:对RuB和TcB而言WC型结构更稳定,WC型结构的RuB具有较大的体弹模量、剪切模量和杨氏模量,说明WC结构的RuB具有优良的弹性性质.计算的电子态密度表明WC型的RuB和TcB均为金属性体系.     

铜微团簇结构及结合能的计算机模拟

铜团簇具有奇异的性质,在催化、纳米技术和大规模集成电路制造中有巨大的应用潜力.采用相对论有效原子实势模型(RECP),在密度泛函方法(DFT)下,使用Gaussian软件,研究了铜微团簇Cun(n=2,…,10)在稳态下的结构和结合能,得到了Cun(n=2,…1,0)的结合能和基态结构,发现随着n的增大,Cun(n=2,…,10)平均结合能会逐步微幅增加(极少数个体例外).