InSi_n(n=2-15)团簇结构、稳定性与电子性质的理论研究

使用卡里普索(CALYPSO)结构预测程序并结合密度泛函理论,在B3LYP/GENECP基组水平上,对InSi_n(n=2-15)团簇的几何结构进行优化与计算.结构优化表明:InSi_n团簇的最低能量构型趋于立体结构(n2),且形成In原子戴帽InSi_(n-1)团簇结构.稳定性分析发现InSi_(12)团簇为幻数结构,In原子的掺杂降低了Si_(n+1)团簇的稳定性.团簇中的电荷总是由In原子向Si原子转移.最后讨论了团簇的电子局域密度函数、红外与拉曼光谱.     

Rhn,Ptn(n=2～20)团簇基态结构的遗传算法研究

用遗传算法结合Gupta紧束缚模型势研究了Rhn, Ptn(n=2～20)团簇的最低能量结构.当n≤13时,两种团簇具有相似的几何结构,都从密堆积结构向二十面体结构演化;当n＞13时,铑团簇的基态结构倾向于有序结构,而铂团簇的基态结构则倾向于无序结构.Rhn, Ptn(n=2～20)团簇中每个原子的平均束缚能和配位数随团簇尺寸的增加而增大.能量的二阶差分给出Rhn, Ptn(n=2～20)团簇的幻数是4,6,13,15.     

AgBr和AgI团簇结构的研究

采用遗传算法结合经验势函数,研究了(AgX)n(X=Br,I,n≤15)团簇的可能稳定结构.结果表明(AgBr)n团簇的稳定结构主要以密堆结构为主,(AgI)n团簇的稳定结构主要以四元环和六元环相接的笼状结构为主.反映出(AgBr)n团簇以离子键结合,而(AgI)n团簇中是具有离子性的共价键.(AgBr)n(n=4,6,10)和(AgI)n(n=6,8,11)的结构较为稳定.     

密度泛函理论对CdnTen（1≤n≤12）团簇结构与性质的研究

采用基于密度泛函理论的DMol3软件包对CdnTen（1≤n≤12）团簇的几何结构进行优化,并对其能量、频率以及电子性质进行模拟分析. 结果表明,团簇CdnTen（1≤n≤12）与团簇CdnSen（1≤n≤12）具有相似的最低能量结构：当n=1～3时,团簇的最低能量结构是平面结构;当n=4～12时,团簇的最低能量结构可以看成是由Cd2Te2和Cd3Te3团簇的最低能量结构组成的三维笼状结构;当n=12时,Cd12Te12团簇的最低能量结构为一个完美的球壳. 随着团簇尺寸的增大,转移的电荷逐渐增加,转移的电荷量有达到块体中电荷值的趋势. 团簇的总能量二阶有限差分,平均结合能以及能隙都显示团簇的幻数为Cd3Te3,Cd6Te6 和Cd9Te9.     

Al_nCl(n=2～14)团簇结构与光谱性质的密度泛函理论研究

在卡里普索(CALYPSO)结构预测方法的基础上,运用密度泛函理论(DFT)中的杂化密度泛函B3LYP,在6-311G+(d)基组水平上,对AlnCl(n=2~14)团簇进行了几何构型优化与电子性质计算。同时,讨论了AlnCl(n=2~14)团簇的平均结合能、能级间隙、二阶能量差分、解离能等性质随着团簇尺寸的演化规律以及红外、拉曼光谱的性质。研究结果表明AlnCl(n=2~14)团簇基态结构由平面结构向三维立体结构演化,形成Cl原子戴帽的Aln-1Cl团簇基态结构,Al7Cl是团簇的幻数结构,AlnCl(n=2~14)团簇的红外振动峰在高频段上只有一个较强的振动峰,而拉曼活性谱图显示,拉曼强振动峰个数较多,并且在中低频段内活性较高。     

AlnCl(n=2-14)团簇结构与电子性质的理论研究

运用卡里普索(CALYPSO)结构预测方法,在杂化密度泛函B3LYP/6-311G+(d)基组水平上,对AlnCl(n=2-14)团簇的几何结构与电子性质进行优化计算,并讨论了团簇的平均结合能、能隙、二阶能量差分、电离能、亲和能以及电子自然布局和极化率。研究结果表明：AlnCl(n=2-14)团簇的基态构型由简单平面几何结构向立体结构演化,形成Cl原子戴帽Aln-1Cl团簇结构;Cl原子的掺杂增大了Aln团簇的平均结合能;二阶能量差分、能隙、电离能、亲和能的变化表明Al7Cl是幻数团簇结构;团簇中的电荷总是由Al原子向Cl原子转移,原子之间的成键作用随着团簇尺寸的增大而增强。     

Al_nCl(n=2-14)团簇结构与电子性质的理论研究

运用卡里普索(CALYPSO)结构预测方法,在杂化密度泛函B3LYP/6-311G+(d)基组水平上,对Al_nCl(n=2-14)团簇的几何结构与电子性质进行优化计算,并讨论了团簇的平均结合能、能隙、二阶能量差分、电离能、亲和能以及电子自然布居和极化率.研究结果表明:Al_nCl(n=2-14)团簇的基态构型由简单平面几何结构向立体结构演化,形成Cl原子戴帽Al_n-1Cl团簇结构;Cl原子的掺杂增大了Al_n团簇的平均结合能;二阶能量差分、能隙、电离能、亲和能的变化表明Al_7Cl是幻数团簇结构;团簇中的电荷总是由Al_原子向Cl原子转移,原子之间的成键作用随着团簇尺寸的增大而增强.     

密度泛函理论对Cd_nTe_n(1≤n≤12)团簇结构与性质的研究

采用基于密度泛函理论的DMol 3软件包对CdnTen(1≤n≤12)团簇的几何结构进行优化,并对其能量、频率以及电子性质进行模拟分析.结果表明,团簇CdnTen(1≤n≤12)与团簇CdnSen(1≤n≤12)具有相似的最低能量结构:当n=1～3时,团簇的最低能量结构是平面结构;当n=4～12时,团簇的最低能量结构可以看成是由Cd2Te2和Cd3Te3团簇的最低能量结构组成的三维笼状结构;当n=12时,Cd12Te12团簇的最低能量结构为一个完美的球壳.随着团簇尺寸的增大,转移的电荷逐渐增加,转移的电荷量有达到块体中电荷值的趋势.团簇的总能量二阶有限差分,平均结合能以及能隙都显示团簇的幻数为Cd3Te3,Cd6Te6和Cd9Te9.     

锌、镉和汞二价负离子团簇的结构和芳香性研究

采用密度泛函理论,在B3PW91/LANL2DZ水平上对二价阴离子Znn2-、Cdn2-和Hgn2- (n=3—7)团簇的稳定结构、芳香性和电子结构进行了研究.研究结果表明:锌、镉和汞团簇的二价阴离子随着n增大其稳定性依次减弱.对于锌团簇来说,当n为奇数时具有较强芳香性,当n为偶数时芳香性较弱或呈现反芳香性,镉团簇和汞团簇的芳香性随着n值增大逐渐减小并最终向反芳香性转变.     

Tin-mZrmO2n(n=2-7，0≤m≤n)团簇结构和稳定性研究

应用密度泛函理论中的B3LYP方法对Tin-mZrmO2n (n = 2-7,0≤m≤n) 团簇的基态几何结构、相对稳定性和电子结构进行了理论研究.结果表明,与桥氧链接的Ti原子被Zr原子取代后形成的混合团簇较为稳定;在团簇尺寸一定的条件下（即n相同）,随着Zr原子数m的增加,团簇的结合能基本呈线性增大,团簇的稳定性增强;Ti、Zr、O原子之间发生了电荷转移现象,形成了稳定的Ti-O-Zr键.     

Guided-Wave Two-Dimensional Acousto-Optic Scanner Using Proton-Exchanged Lithium Niobate Waveguide

Two-dimensional scanning of a 0.6328 mum guided-light beam has been realized using noncolinear acousto-optic (AO) coplanar Bragg diffraction together with colinear AO guided-mode to substrate radiation-mode conversion in a Z-cut Xpropagation LiNbO3 proton-exchanged (PE) waveguide. The two surface acoustic (SAW) waves utilized are at the center frequencies of 500 and 200 MHz, propagating in the Y and X axes, respectively. Two-dimensional scanning of approximately 720 resolvable light beam spots, namely, 18 40 (horizontal vertical) scanning, has been demonstrated using a light beam of 1.0 mm aperture. The total number of resolvable beam spots can be greatly increased from 720 by simply utilizing SAW transducers of larger bandwidth and a light beam of greater aperture. It should also be possible to significantly increase the diffraction efficiency from 3 % by optimizing the parameters of the PE waveguide and the SAWs.     

Effect ofγ-radiation on the spectral luminescence characteristics of impure cadmium tungstate crystals

Results of a study of the effect of γ-radiation on the spectral luminescence properties of cadmium tungstate crystals doped with silver, bismuth, and molybdenum cations are presented. Spectral characteristics of the nondnnnoped crystals are briefly described. Absorption and photo and X-ray luminescence spectra of the crystals taken before and after exposure to γ-radiation (5.5·10⁴ Gy) are compared. It is found that the spectral characteristics of the crystals doped with silver, bismuth, and molybdenum cations do not change markedly after the exposure. The relation between the type of impurity-induced defects, individual characteristics of the impurity cations, and the character of the effect of γ-radiation on the spectral luminescence properties of impure crystals is analyzed (preliminarily). Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 64, No. 1, pp. 55–60, January–February, 1997.     

Femtosecond Transform-Limited Pulse Generation by Compensating for the Linear Chirp of SPM Spectra in Dispersion Shifted Fibers

A simple technique of pulse compression, based on the linear chirp compensation of self-phase modulation (SPM) spectra in dispersion shifted fibers, is demonstrated. The optimization procedure is carried out, for a short span of a single-mode fiber, using a parabolic law, which describes the behavior of the squared output pulse width versus the pump peak power in the case of Gaussian pulses. The experimental results give a minimum pulse duration of 233 fs, which is in good agreement with the model. Shorter and coherent pulses, down to 90 fs, have been obtained by inserting an interference filter at the optical output.     

Sorting of bending magnets for the SSRF booster

The Shanghai Synchrotron Radiation Facility(SSRF)booster ring,a full energy injector for the storage ring,is deigned to accelerate the electron beam energy from 150MeV to 3.5GeV that demands high extraction efficiency at the extraction energy with low beam loss rate when electrons are ramping.Closed orbit distortion(COD)caused by bending magnet field uniformity errors which affects the machine performance harmfully could be effectively reduced by bending magnet location sorting.Considering the affections of random errors in measurement,both ideal sorting and realistic sorting are studied based on measured bending magnet field uniformity errors and one reasonable combination of bending magnets which can reduce the horizontal COD by a factor of 5is given as the final installation sequence of the booster bending magnets in this paper.     

Measurement of nonlinear coefficient of optical fiber based on small chirped soliton transmission

We measure the waveform and phase curves of short optical pulses before and after transmission over different lengths of fibers by use of the pulse analyzer with the frequency-resolved optical gating (FROG),and numerically simulate pulse evolution under the experimental conditions.The nonlinear coefficient of the fiber is given by comparing the experimental results with the numerical ones.Difference between the experiment and numerical simulation is analyzed.     

Resonance scattering of canonical elastic shells in absorbing fluid medium

Resonance scattering of elastic spherical shell and cylindrical shell while the surrounding fluid medium has absorption is studied. The normal mode solution derived using exact elastic theory and the separation of variables is still applicable. However, the scattering form function has to be modified for the absorbing medium, otherwise the unreasonable result would be obtained. The backscattering form function in the absorbing medium is redefined, and the form function of elastic spherical and cylindrical shell with vacuum or solid matter filled is calculated in various absorption conditions. The results show that the absorption of surrounding fluid leads to notable attenuation of the coincidence resonances in the mid-frequency, but it has a little influence on the low-frequency resonance scattering induced by the filler inside the shell.     

Single-beam self-referenced phase-sensitive surface plasmon resonance sensor with high detection resolution

A versatile and low-cost single-beam self-referenced phase-sensitive surface plasmon resonance(SPR)sensing system with ultra-high resolution performance is presented.The system exhibits a root-mean-square phase fluctuation of ±0.0028.over a period of 45 min.i.e.a resolution of±5.2×10-9 refractive index units.The enhanced performance has been achieved through the incorporation of three design elements:a true single-beam configuration enabling complete self-referencing so that only the phase change associated with SPR gets detected,a differential measurement scheme to eliminate spurious signals not related to the sensor response,and the elimination of retardation drifts by incorporating temperature stabilization in the liquid crystal phase modulato .Our design should bring the detection sensitivity of non-labeling SPR biosensing closer to that achievable by conventional fluorescence-based techniques.     

Influences of SiO2 protective layers and annealing on the laser-induced damage threshold of Ta2O5 films

Ta2O5 films are prepared on BK7 substrates with conventional electron beam evaporation deposition.The effects of SiO2 protective layers and annealing on the laser-induced damage threshold (LIDT) of the films are investigated.The results show that SiO2 protective layers exert little influence on the electric field intensity(EFI)distribution,microstructure and microdefect density but increase the absorption slightly.Annealing iS effective on decreasing the microdefect density and the absorption of the films.Both SiO2 protective layers and annealing are beneficial to the damage resistance of the films and the latter is more effective to improve the LIDT.Moreover,the maximal LIDT of Ta2O5 films is achieved by the combination of SiO2 protective layers and annealing.     

A stereo matching algorithm using multi-peak candidate matches and geometric constraints

Gray cross correlation matching technique is adopted to extract candidate matches with gray cross correla- tion coefficients less than some certain range of maximal correlation coefficient called multi-peak candidate matches. Multi-peak candidates are extracted corresponding to three closest feature points at first. The corresponding multi-peak candidate matches are used to construct the model polygon. Correspondence is determined based on the local geometric relations between the three feature points and the multi-peak candidates. The disparity test and the global consistency checkout are applied to eliminate the remaining ambiguous matches that are not removed by the local geometric relational test. Experimental results show that the proposed algorithm is feasible and accurate.