4-氨基-3,5-二硝基吡唑二聚体分子间相互作用的理论研究（英文）

在密度泛函(DFT)B3LYP/6-311++G~(**)水平下,求得4-氨基-3,5-二硝基吡唑(LLM-116)二聚体势能面上的4种全优化几何构型.经基组叠加误差(BSSE)和零点能(ZPE)校正,求得分子间最大相互作用能为-29.56 k J·mol~(-1).研究表明,其相互作用是放热过程,并随着温度的升高,相互作用减弱;自然键轨道(NBO)分析揭示了相互作用的本质;对优化构型进行振动分析,得其红外光谱,并基于统计热力学求得200.0-800.0 K温度范围从单分子形成二聚体的热力学性质变化.     

4-氨基-3,5-二硝基吡唑二聚体分子间相互作用的理论研究

在密度泛函（DFT）B3LYP/6-311++G**水平下,求得4-氨基-3,5-二硝基吡唑（LLM-116）二聚体势能面上的4种全优化几何构型。经基组叠加误差（BSSE）和零点能（ZPE）校正, 求得分子间最大相互作用能为 –29.56 kJ×mol-1。研究表明,其相互作用是放热过程,并随着温度的升高,相互作用减弱;自然键轨道（NBO）分析揭示了相互作用的本质;对优化构型进行振动分析,得其红外光谱,并基于统计热力学求得200.0-800.0 K 温度范围从单分子形成二聚体的热力学性质变化。     

O3与O3分子间相互作用的理论研究

采用从头算方法,在B3LYP水平下对O3分子单体及其二聚体进行了几何结构优化,得到四种O3分子二聚体的稳定构型,并经MP2法、均衡法(Massage)分别校正了电子相关和基组叠加误差(BSSE),通过对分子中原子间的最短距离,分子间质心距离与各构型相互作用能的关系进行了分析、比较,得到了最稳定的构型,其对应的O3分子二聚体相互作用能为:-8.788 kJ/mol.     

HOX(X=F,Cl)二聚体红移氢键的理论研究

用理论方法研究了二聚体HOX(X=F,Cl)分子间氢键,在B3LYP/6-31+G(d,p)、 B3LYP/6-311++G(d,p)、MP2/6-31+G(d,p)和MP2/6-311++G(d,p)水平上,利用标准方法和均衡校正方法对二聚体进行了几何优化、振动频率和相互作用能的计算。同时,利用电子密度拓扑分析和自然键轨道分析对红移氢键的本质进行了分析。研究表明：分子间O—H…O和O—H…X(X=F,Cl)氢键的形成使二聚体中O—H键伸长,伸缩振动频率减小,形成红移氢键。NBO分析表明,电荷转移效应占优势,因此形成O—H…O和O—H…X(F,Cl)红移氢键。     

甲醛与甲酰胺相互作用的从头算研究

在MP2 /6 3 1G(d)和MP2 (FC) /6 3 11+ +G(d ,p)水平上 ,对H2 CO和HCONH2 以及设计的 3种构型H2 CO…HCONH2 复合物等进行几何全优化计算 ,经振动频率分析 ,确认它们为势能超曲面上的稳定驻点 .然后在MP2 /6 3 11+ +G(2df,3p)水平上进行单点能计算和基组重叠误差 (BSSE)校正以获得相互作用能 .并利用自然键轨道理论和分子中的原子理论探讨H2 CO和HCONH2 相互作用的本质 .分子间相互作用的能量分解分析显示 ,静电能在H2 CO…HCONH2 相互作用能中占主导地位     

环五甲撑五硝胺(CRX)结构和性质的DFT预示

用密度泛函理论 (DFT)B3LYP方法 ,在 6 31G 基组水平下 ,全优化计算了环五甲撑五硝胺 (CRX)的分子几何和优化构型下的电子结构 .环C -N键长为 0 .144～ 0 .148nm ,N -NO2 键长为 0 .139～ 0 .142nm ;CRX的最高占有MO(HOMO)能级和最低未占MO(LUMO)能级之间的差值ΔEg(5 .2 0 5 4eV)较大 ,预示CRX较稳定 .基于简谐振动分析求得IR谱频率和强度 .运用统计热力学方法 ,求得在 2 0 0～ 12 0 0K的热力学性质C0p ,m、S0 m 和H0 m.还运用Kamlet公式预示了它的爆速和爆压分别为 916 9m/s和 37.88GPa .     

3-呋喃甲酸红外光谱及分子间相互作用的理论研究

采用密度泛函理论(DFT)B3LYP/6-311+G(d, p)及二级微扰理论(MP2)MP2/6-311G+(d, p)对3-呋喃甲酸单分子进行构型优化,得到了该分子的两个稳定几何构型,通过计算异构化反应的过渡态,构型Ⅰ转变为构型Ⅱ要克服32.10 kJ·mol~(-1)势垒,异构化反应常温下较难进行。玻尔兹曼分布结果表明常温下低能量的构型Ⅰ百分含量远高于高能量的构型Ⅱ,故常温下以构型Ⅰ的形式存在。在此基础上采用非谐性力场计算了单分子的红外光谱,并计算了振动频率的势能分配比例,指认了相应的振动模式,发现单分子的计算数据与实际气相分子的红外谱图相似,对2 000～2 500 cm~(-1)出现的吸收峰可采用倍频、和频给以解释。对于二聚体,采用考虑分子间弱相互作用校正的M06密度泛函进行模拟,非谐性条件下二聚体的计算结果与固态谱图较为相符, 2 000～3 000 cm~(-1)之间出现的弱吸收峰,对应各种泛频峰,经计算振动量子数对应的0→2红外跃迁的倍频吸收峰强度很小,而基频之间形成的合频是造成这些峰的主因,由于二聚体分子间是通过氢键而不是化学键结合的,其刚性降低,非谐性因素增大,与之相关的合频峰的强度也随之增大,在单体中不太明显的这些峰在二聚体中已很明显,与实验谱图较为吻合。但实际固体中由于存在多种二聚体、多聚体,使得羟基的红外吸收峰变宽且强度降低,另外量子化学理论由于缺乏精准的弱相互作用的计算参数、普适的力场、合理的色散校正项等因素,使得计算结果与实际谱图有一定差距。进一步对该分子的二聚体进行了自然键轨道分析,发现电子给体羰基氧原子与电子受体羟基形成的二级稳定化能为121.4 kJ·mol~(-1),分子间结合能为65.27 kJ·mol~(-1),给体反馈到受体轨道的电荷为0.067个电荷,表明3-呋喃甲酸分子间的相互作用主要来自于形成的分子间氢键。通过计算不同温度下二聚体的吉布斯自由能变,当温度升高到500 K时ΔG值变为正值,二聚体变得不稳定,氢键被破坏,单体分子将以分子间作用力结合在一起。     

ThO+/0/-2不同电荷态对N2O氧化CO反应的影响

本文采用密度泛函理论,对ThO^+/0/-₂团簇参与CO与N₂O间氧化还原反应(CO+N₂O→CO₂+N₂)的机理展开研究,探讨钍氧团簇所带的电荷对该反应的影响.研究表明：ThO^+/0/-₂在反应中主要起传输氧原子的作用,其中ThO⁺₂与CO的反应以及ThO^+/0/-与N₂O的反应都为热力学上的放热反应,而ThO^0/-₂与CO的反应为热力学上的吸热反应.随着电荷态的改变,ThO^+/0/-₂与CO反应的总能垒(E_b)与总驱动力(-ΔG)有较大差异.因此,通过改变ThO₂的电荷态能调节其对CO/N₂O反应的催化活性,综合考虑,ThO⁺₂对...     

硼、氮取代二聚苯中碳原子导致层间相互作用本质变化研究

在MP2/aug-cc-pVTZ水平下优化了二聚苯及其碳被硼、氮原子取代的几何构型;计算了这些二聚体的CCSD(T)/CBS相互作用能;并用SAPT2+/aug-cc-pVDZ分析了相互作用能成分.探索了硼、氮取代二聚苯中碳原子所导致层间相互作用本质变化.结果表明:稳定构型而言,从苯(C_6H_6)、1-氮-2-硼杂苯(BNC_4H_6)、1,3-二氮-2,4-二硼杂苯(B_2N_2C_2H_6)二聚体的平行移位(PD)构型向无机苯(B_3N_3H_6)二聚体的夹心(S)构型转变,其中C_6H_6和B_3N_3H_6二聚体稳定构型的堆叠型式分别与之相对应的石墨烯(GE)和六方氮化硼(h-BN)2D层间材料的堆叠型式相一致.硼、氮原子取代二聚苯中的碳原子后使其相互作用能增大,其中BNC_4H_6和B_2N_2C_2H_6二聚体的相互作用能增大较为明显.所研究体系二聚体稳定构型均以色散能为主导、静电能次之、诱导能相对较小.硼、氮取代二聚苯中碳原子后其静电能对总吸引能的贡献明显增大.     

HArF和HNO二聚体相互作用氢键的理论研究

用二阶微扰理论结合6-311+G**、6-311++G**和6-311++G(2d,2p)基组对氢键相互作用二聚体HNO···HArF进行研究．在MP2/6-311+G**、MP2/6-311++G**和MP2/6-311++G(2d,2p)水平上，利用标准方法和均衡校正方法对二聚体进行了几何优化、振动频率和相互作用能的计算．对于相互作用能采用G2MP2方法计算．计算结果表明存在两种稳定的二聚体HNO···HArF结构，在这两种结构中，Dimer I(H···F)比Dimer II(H···O)更加稳定．通过振动频率的计算表明，在Dimer I(H···F)中存在N-H···F蓝移氢键，在DimerII(H···O)中存在Ar-H···O红移氢键，并对蓝移氢键加以确认．利用电子密度拓扑学分析和自然键轨道分析对于氢键红移和蓝移进行了合理解释．     

Theoretical analysis and simulation of conjugate heights for dual-conjugate AO system in lidar

A multi-conjugate adaptive optics （MCAO） can offer a possibility of widening field of view （FOV） characterized by the isoplanatic angle, and the choose of conjugate height becomes a basic problem for MCAO, which influences the size of iosplanatic angle. Considering the application of lidar, the isoplanatic angle＇s expressions of two deformable mirrors （DMs） MCAO for uplink and downlink are deduced. The effects of conjugate heights for dual-conjugate AO are thoughtfully discussed, and the isoplanatic angles are further analyzed. The results show that the isopanatic angle varies with the conjugate height and reaches the maximum as the conjugate height is at the optimal altitude. Moreover, the optimal conjugate height changes with the propagation distance.     

Quick single-photon detector with many avalanche photo diodes working on the time division

Due to the limit of response speed of the present single-photon detector, the code rate is still too low to come into practical use for the present quantum key distribution (QKD) system.A new idea is put up to design a quick single-photon detector.This quick single-photon detector is composed of a multi-port optic-fiber splitter and many avalanche photo diodes (APDs).Au of the ports with APDs work on the time division and cooperate with a logic discriminating and deciding unit driven by the clock signal.The operation frequency lies on the number N of ports, and can reach N times of the conventional single-photon detector.The single-photon prompt detection can come true for high repetition-rate pulses.The applying of this detector will largely raise the code rate of the QKD, and boost the commercial use.     

Characterization of PolyA and PolyC mismatches by Raman spectroscopy

A.C mismatches are studied by Raman spectral characterization of PolyA, PolyC, and their equimolar complex in solution of 0.14 mol/L Na ,pH7.0.Experimental results show that A·C mismatches occur to be A/B (mainly A) conformers, and unlike Watson-Crick base pairing, this kind of mismatches is stabilized by only one hydrogen bond involving cytosine N4H2 and adenine N7.The formation of A·C complex makes the base stacking interactions much stronger, and conformation of the backbone more ordered, which leads to obvious Raman hypochromic effect with some shifts in corresponding bands.     

Improvement of four-wave mixing-based wavelength conversion efficiency in dispersion shifted fiber by 40-GHz clock pumping

40-GHz clock modulated signal as a pump to improve the efficiency of four-wave mixing (FWM)-based wavelength conversion in a 26.5-km dispersion shifted fiber (DSF) is investigated. The experimental results demonstrate that the conjugated FWM component has higher intensity with the clock pumping than that with the continuous-wave (CW) light pumping. The improvement of FWM-based wavelength conversion efficiency is negligible when the pump power is less than Brillouin threshold. But when the pump power is greater than Brillouin threshold, the improvement becomes significant and increases with the increment of pump power. The improvement can increase up to 9 dB if pump power reaches 17 dBm.     

Multi-pulse operation of a Kerr-lens mode-locked femtosecond laser

Our experimental results show that the presence of a proper amount of negative group velocity dispersion is essential to multi-pulse operation of a Kerr-lens mode-locked femtosecond laser. We demonstrate that the pulse separations and the number of pulses contained within a cavity round trip are strongly dependent on the initial perturbations. The results allow us to get a better understanding on the influences of the convoluted self-phase modulation and intra-cavity dispersions on the stable multi-pulse oscillation in a Kerr-lens mode-locked femtosecond laser.     

Propagation of Helmholtz-Gauss beams in weak turbulent atmosphere

Based on the Rytov approximation of light propagation in weak turbulent atmosphere,the closed-form expressions of field and average irradiance of each one of the four fundamental families of Helmholtz-Gauss (HzG)beams:cosine-Gauss beams,stationary Mathieu-Gauss beams,stationary parabolic-Gauss beams,and Bessel-Gauss beams,which are propagating in weak turbulent atmosphere,are obtained.The results show that the field and average irradiance can be written as the product of four factors:complex amplitude depending on the z-coordinate only,a Ganssian beam.a factor of complex phase perturbation induced by atmospheric turbulence,and a complex scaled version of the transverse shape of the non-diffracting beam.The effect of weak atmospheric turbulence on irradiance distribution of the HzG beam can be ignored.     

An effective method for reducing speckle noise in digital holography

An effective method for reducing the speckle noise in digital holography is proposed in this paper.Different from the methods based on classical filtering technique,it utilizes the multiple holograms which are generated by rotating the illuminating light continuously.The intensity images reconstructed by a series of holograms generated by rotating the illuminating light possess different speckle patterns.Hence by properly averaging the reconstructed intensity fields,the speckle noises can be reduced greatly.Experimental results show that the proposed method is simple and effective to reduce speckle noise in digital holography.     

Influence of purity of HfO2 on reflectance of ultraviolet multilayer

The impurities in two kinds of HfO2 materials and in their corresponding single layer thin films were determined through glow discharge mass spectrum technology and secondary ion mass spectrometry(SIMS) equipment respectively.It was found that ZrO2 was the main impurity in the two kinds of HfO2 either in the original HfO2 materials or in the electron beam deposited films.In addition,the difference of Zr content in the two kinds of HfO2 single laver films was much laxger than that of the other impurities such as Ti and Fe.which showed that it was just ZrO2 that made the difference between the optical performance of the film products including the two kinds of HfO2.With these two kinds of HfO2 and the same kind of SiO2.we deposited HfO2/SiO2 multilayer reflective coatings at the wavelength of 266 nm.Experimental results showed that the reflectances of these two mirrors were about 99.85% and 99.15% respectively,which agreed well with the designed results what were based on the optical constants obtained from the corresponding single layer thin films.     

Speech enhancement by array crosstalk resistant ANC and spectrum subtraction

Microphone array-based speech enhancement has great importance for speech communications and speech recognition. To reduce the aperture of the microphone array and to increase the effect of the speech enhancement will greatly broaden the application areas of the microphone array. An array crosstalk resistant adaptive noise cancellation method is therefore presented. And then an improved spectral subtraction algorithm is further cascaded to obtain better enhancement results. Theoretic analysis and experiments indicate that the proposed scheme needs only a very small microphone array while it simultaneously achieves a higher SNR improvement. Besides, the proposed scheme can be used in many noisy environments and is easy for real-time implementation.