空位浓度对纤锌矿BN电子结构和光学性质影响的第一性原理研究

本文采用了第一性原理研究了空位缺陷纤锌矿BN的电子结构和光学性质.通过对能带结构、态密度分析发现：缺陷体系由于B、N的缺失,费米能级附近出现杂质能级.相较于本征体系,随着空位浓度增加,杂质能级变多,跃迁能量减小. N空位缺陷的纤锌矿BN态密度总体向低能区移动,且能级相较于B空位缺陷的纤锌矿BN明显增多.从复介电函数和光学吸收谱分析中发现,随着空位浓度的增加,缺陷体系纤锌矿BN在可见光区域的吸收逐渐增强.尤其是B₂₂N₂₄在可见光区域出现的吸收效果更好.     

高压下ZnTe的电子结构和光电性质

应用第一性原理平面波赝势计算方法,研究了闪锌矿ZnTe晶体在外界压力下的电子结构和光电性质,并计算了介电函数和光学吸收系数随压力的变化情况。结果表明:在高压作用下,Te原子和Zn原子的态密度分布都向低能量方向移动,分布范围增大,Te 5p和Zn3d电子轨道杂化变强。随着压力的增大,直接带隙逐渐增大,而间接带隙逐渐变小。当压力为10.7GPa时,能带结构从直接带隙转变为间接带隙结构。压力增大,有利于Te 5p与Zn3d电子间的跃迁,光吸收系数增大,产生更多的电子-空穴对,材料导电能力增强。     

ZnS掺Ag与Zn空位缺陷的电子结构和光学性质

本文基于第一性原理平面波赝势(PWP)和广义梯度近似(GGA)方法,对ZnS闪锌矿结构本体、掺入p型杂质Ag和Zn空位超晶胞进行结构优化处理. 计算了三种体系下ZnS材料的电子结构和光学性质,并从理论上给出了p型ZnS难以形成的原因. 详细分析了其平衡晶格常数、能带结构、电子态密度分布和光学性质.结果表明:在Ag掺杂与Zn空位ZnS体系中,由于缺陷能级的引入,禁带宽度有所减小,在可见光区电子跃迁明显增强. 关键词： 硫化锌 缺陷 电子结构 光学性质     

空位缺陷及Mg替位对纤锌矿(Ga,Mn)N电子结构和磁光性能的影响

采用自旋密度泛函理论框架下的广义梯度近似(GGA+U)平面波超软赝势方法,构建了未掺杂纤锌矿GaN超胞、三种不同有序占位Mn双掺GaN,(Mn,Mg)共掺杂GaN以及存在空位缺陷的Mn掺杂GaN超胞模型,分别对所有模型的能带结构、电子态密度、能量以及光学性质进行了计算.计算结果表明:与纯的GaN相比,Mn掺杂GaN体系的体积略有增大,掺杂体系居里温度能够达到室温以上;随着双掺杂Mn-Mn间距的增大,体系总能量和形成能升高、稳定性下降、掺杂越难;(Mn,Mg)共掺杂并不能有效增大掺杂体系磁矩,也不能达到提高掺杂体系居里温度的作用;Ga空位缺陷和N空位缺陷的存在不利于Mn掺杂GaN形成稳定的铁磁有序.此外,Mn离子的掺入在费米能级附近引入自旋极化杂质带,正是由于费米能级附近自旋极化杂质带中不同电子态间的跃迁,介电函数虚部在0.6868eV附近、光吸收谱在1.25eV附近分别出现了一个较强的新峰.     

In掺杂ZnTe发光性能的第一性原理计算

利用基于密度泛函理论的第一性原理对In掺入ZnTe半导体后引入的各种缺陷进行了结构优化、 能带和态密度分析及转换能级的计算. 计算结果表明: 掺杂后体系中主要存在两种缺陷, 一种是In原子替换了Zn原子的置换型缺陷; 另一种是由In替换Zn后再与临近的Zn空位形成的复合缺陷. 二者分别在导带底下方0.26 eV和价带顶上方0.33 eV的位置形成各自的转换能级. 电子在这两个转换能级之间跃迁辐射出的能量大小与实验测量到的能量大小相符, 解释了原本发绿光的ZnTe在掺入In后发出近红外光的根本原因. 关键词： ZnTe 半导体掺杂 近红外光 第一性原理     

第一性原理研究Fe掺杂SnO2材料的光电性质

采用基于第一性原理的线性缀加平面波(FP-LAPW)方法,研究Fe掺杂SnO₂材料电子结构和光学性质,包括电子态密度、能带结构、介电函数和其他一些光学图谱. 研究结果表明,掺Fe后材料均属于直接跃迁半导体,且呈现半金属性;随掺杂浓度增加,费米能级进入价带,带隙逐渐减小,Fe原子之间耦合作用增强;通过掺杂能够在一定程度上改变成键性质,使其具有金属键性质. 光学谱线(吸收谱、消光系数等)与介电函数虚部谱线相对应,均发生蓝移,各峰值与电子跃迁吸收有关,从理论上指出光学性质和电子结构的内在联系. 关键词： 能带结构 态密度 光学性质 介电函数     

掺杂ZnTe对电子结构与磁性质的影响

为了研究Mn、Fe、Co、Ni掺杂ZnTe的电子结构和磁性的相关性质.本文基于第一性原理的数值基组的方法计算了Mn、Fe、Co、Ni掺杂ZnTe的能带结构、态密度,分析了掺杂结构的稳定性和磁性性质.结果发现Mn、Fe、Co、Ni掺杂ZnTe的杂质替换能分别为-1.14 e V,-1.23 e V,39.95 e V,-4.32 eV,表明Mn、Fe、Ni掺杂的ZnTe在实验上较容易实现.Mn、Co掺杂ZnTe导致体系产生的总磁矩分别为0.997μB,1.103μB,其中磁性的主要来源于Mn、Co原子在Zn位的取代而引起,产生局域磁性主要取决于Mn、Co的d轨道与Te的p轨道耦合作用.     

Fe和Ni共掺杂ZnO的电子结构和光学性质

基于密度泛函理论的第一性原理研究Fe,Ni单掺杂和(Fe,Ni)共掺杂纤锌矿型ZnO的能带结构、电子态密度分布、介电函数、光学吸收系数,分析了掺杂后电子结构与光学性质的变化.计算结果表明：掺杂体系的费米能级附近电子态密度主要来源于Fe 3d,Ni 3d态电子的贡献;与纯净ZnO相比,Fe,Ni单掺杂和(Fe,Ni)共掺杂ZnO的介电函数虚部均在0.46eV左右出现了一个新峰;Fe,Ni单掺杂和共掺杂ZnO的吸收光谱均发生明显的红移,并都在1.3eV处出现较强吸收峰.结合他人的计算和实验结果,给出了定性的讨 关键词： 氧化锌 掺杂 第一性原理 光学性质     

ZnLa_xS_(n-x)(x=4,8)半导体材料光电性质的第一性原理计算

本文采用第一性原理研究了Zn S,Zn La4Sn-4,Zn La8Sn-8三个体系的能带结构、分态密度、总态密度以及复介电函数.研究结果显示:Zn S体系的价带顶和导带底都在G点处,为直接带隙材料;Zn La4Sn-4,Zn La8Sn-8两体系的导带向价带移动,费米能级处有多条能级穿过,费米能级处附近的态密度则由S 3p,Zn3p和La 5d以及5p轨道组成;对比分析Zn S,Zn La4Sn-4,Zn La8Sn-8三个体系的复介电函数的虚部发现Zn La4Sn-4、Zn La8Sn-8体系在0-10e V区域内的介电峰都少于本征结构,而在10到20 e V的高能量区间内,Zn La4Sn-4、Zn La8Sn-8体系介电峰的相应幅度较Zn S增强.     

Fe,Ni掺杂CdS的电子结构和光学性质

基于密度泛函理论（DFT）的第一性原理研究了Fe,Ni单掺杂和（Fe,Ni）共掺杂CdS的能带结构、电子态密度分布、介电常数和光学吸收系数,分析了掺杂后电子结构和光学性质的变化.计算结果表明:掺杂体系的CdS晶格常量均减少,能带宽度减小,介电函数虚部ε₂（ω）都在0.53 eV左右出现了一个新峰,吸收光谱发生明显的红移,它们均在1.35 eV处出现较强吸收峰.     

白光和红绿蓝光LED可调光源研制

为了提高LED光源色温和亮度的调节精度和准确度,结合色温由低向高变化时光色所呈现的渐变特点,提出了一种低色温白光LED灯珠、高色温白光LED灯珠加红绿蓝光LED灯珠补偿式调光的方法.将色温分成三个部分进行调节,每个部分选用不同的LED灯珠组合来进行调光.实验结果表明:不同组合情况下的LED光源的初始输出色温相对于目标值的偏差范围在1％以内;亮度可以在保证色温不变的情况下独立进行调节,初始输出值与目标值的偏差范围在1％以内;经过微调之后可以达到目标值;达到了色温和亮度独立调节的要求;光源发光稳定,不会因为长时间工作而影响调节精度.     

Visualization and interferometry for cylindrical and spherical sample tomography and profilometry

A technique combining image processing and laser interferometry for visualizing and detecting the deformation of transparent cylindrical and spherical sample is proposed. This deformation includes geometric deformation such as volume transition in profilometry and physical deformation such as refractive index change in tomography. Phase contour lines are used for quantitative analysis and graphical representation of the deformation. This method allows us to visually detect the spatial variation of the deformation field and to evaluate the test quality such as misalignment of optical system. A theoretical analysis using phase contour map to characterize the deformation field is described in detail. A method using phase contour map to qualify the interferometric test is proposed. Analysis of test examples is carried out. Suggestions on using phase contour line method to ameliorate test system design are finally discussed.     

Quantum and Classical Disparity and Accord

Discrepancies and accords between quantum (QM) and classical mechanics (CM) related to expectation values and periods are generally found for both the harmonic oscillator (SHO) and a free particle in a box (FPB), which may apply generally. These indicate non-locality is expected throughout QM. The FPB energy states violate the Correspondence Principle. Previously unexpected accords are found and proven that 〈x ²〉 _CM =〈x ²〉 _QM and τ _CM =τ _QMb (beat period i.e. beats between the phases for adjoining energy states) for the SHO for all quantum numbers, n. However, for the FPB the beat periods differ at small n. It is shown that a particle’s velocity in an infinite square well varies, no matter how wide the box, nor how far the particle is from the walls. The quantum free particle variances share an indirect commonality with the Aharonov-Bohm and Aharonov-Casher effects in that there is a quantum action in the absence of a force. The concept of an “Expectation Value over a Partial Well Width” is introduced. This paper raises the question as to whether these inconsistencies are undetectable, or can be empirically ascertained. These inherent variances may need to be fixed, or nature is manifestly more non-classical than expected.     

黑克、布劳、及伯曼-温采尔代数的诱导及分导系数和量子经典李代数的耦合与重新耦合系数

本文总结了计算黑克、布劳、及伯曼 温采尔代数在各种工数链下诱导及分导系数的线性方程方法(LEM)。特别强调了关于A,B,C,D型李代数及其量子情形与其中心代数之间的舒尔 魏尔 布劳双关性关系。这一关系使我们能够利用相应中心代数的诱导及分导系数计算出经典李代数及其量子情形的耦合与重新耦合系数。讨论了从该方法得到B,C,D型李代数不可约表示克罗内克积分解的应用。基于LEM还得到了处理对应于置换群CG系列问题的黑克代数张量积的方法。     

国外超导材料技术研究政策和方向

超导材料技术是21世纪具有战略意义的高新技术,极具发展潜力和市场前景。世界各发达国家纷纷制定研发计划,给予高度重视和大力支持,加快超导材料技术的基础研究和产业化发展。主要从美国、日本、欧洲国家、韩国等国家的相关研发计划、政策以及主要科研机构的研发概况出发,阐明目前国外超导材料技术的研究政策和方向。     

Spectroscopy and Photophysics of Iso- and Alloxazines: Experimental and Theoretical Study

We present a systematic study of the effect of methyl substitution on iso- and alloxazines in acetonitrile solutions. Substitution patterns have profound effects on both spectral and photophysical properties, with fluorescence quantum yields varying by more than an order of magnitude. TD-DFT calculation were used for the first time to correlate electronic structure changes with the substitution patterns, with good agreement between calculated and theoretical band positions and oscillator strengths. Both n-pi* and pi-pi* states in these compounds are predicted, with the oscillator strengths indicating that only the pi-pi* states should be observable in the absorption spectra. Substitution patterns are shown to be responsible for energy order inversion between these states.     

Rapid and flexible laser marking and engraving of tilted and curved surfaces

We present a novel method for rapid and flexible laser marking and engraving of tilted, curved and freeform work-piece surfaces. The method is based on integrating a three-dimensional (3D) laser measurement system into a 3D laser marking system. We use the same laser source and optics for measurement and processing with a minimum of additional hardware components. A low power CW laser regime is used to measure the 3D shape of a work-piece surface while a high-peak power-pulsed laser regime is used for processing. The acquired 3D surface data are used to determine the 3D trajectory of the processing beam focus. Neither the 3D shape of the work-piece nor its orientation needs to be known in advance as long as the processed surface lies within the working range of the 3D laser processing system. This eliminates the need for exact work-piece positioning before processing and substantially improves processing flexibility (allowing, e.g. variations in work-piece shape or/and orientation from mark to mark). This paper discusses key issues concerning an implementation of the method and presents typical examples of markings and engravings, which demonstrate the advantages of the method with respect to the existing industrial 2D and 3D laser marking and engraving methods. The method can also be applied to flexible laser structuring and microprocessing of curved surfaces.     

Geometry and Elasticity of Strips and Flowers

We solve several problems that involve imposing metrics on surfaces. The problem of a strip with a linear metric gradient is formulated in terms of a Lagrangian similar to those used for spin systems. We are able to show that the low energy state of long strips is a twisted helical state like a telephone cord. We then extend the techniques used in this solution to two–dimensional sheets with more general metrics. We find evolution equations and show that when they are not singular, a surface is determined by knowledge of its metric, and the shape of the surface along one line. Finally, we provide numerical evidence by minimizing a suitable energy functional that once these evolution equations become singular, either the surface is not differentiable, or else the metric deviates from the target metric.     

Divergence- and Curl-Preserving Prolongation and Restriction Formulas

We present new second-order prolongation and restriction formulas which preserve the divergence and, in some cases, the curl of a discretized vector field. The formulas are suitable for adaptive and hierarchical mesh algorithms with a factor-of-2 linear resolution change. We examine both staggered and collocated discretizations for the vector field on two- and three-dimensional Cartesian grids. The new formulas can be used in combination with numerical schemes that require a divergence-free solution in some discrete sense, such as the constrained transport schemes of computational magnetohydrodynamics. We also obtain divergence-preserving interpolation functions which may be used for streamline or field line tracing.