二甲基亚锗基锗烯与乙醛生成螺锗杂环化合物反应机理的密度泛函理论研究

用B3LYP/6-31G*方法研究了单重态二甲基亚锗基锗烯(Me₂Ge=Ge:)与乙醛环加成反应的反应机理,根据该反应的势能面可以预言,该反应有一条主反应通道. 该反应所呈现的反应规律为：两反应物通过[2+2]环加成反应首先生成了一锗杂四元环锗烯,由于该锗杂四元环锗烯中Ge:原子的4p空轨道与乙醛的?轨道形成了π→p授受键,从而使锗杂四元环锗烯进一步与乙醛结合生成了一中间体. 由于该中间体中的Ge:原子在过渡态之后发生了sp³杂化,从而使该中间体经过渡态异构化为了一螺锗杂环化合物. 该研究结果从理论上揭示了单重态二甲基亚锗基锗烯(Me₂Ge=Ge:)与乙醛环加成反应的反应机制,奠定了亚锗基锗烯(H₂Ge=Ge:)及其衍生物(X₂Ge=Ge:, X=H, Me, F, Cl, Br, Ph, Ar?)与非对称性π键化合物环加成反应的理论基础.     

Density Functional Theory Study of Mechanism of Cycloaddition Reaction Between Dimethyl-Silylene Carbene and Acetone

用密度泛函理论研究了单重态二甲基亚硅基卡宾与丙酮环加成反应的反应机理,势能面结果表明该反应有两条相互竞争的主反应通道. 反应规律为：二甲基亚硅基卡宾中的π轨道与π键化合物中π轨道的[2+2]环加成作用造成了扭曲四员环中间体和平面四员环产物的形成;平面四员环产物中卡宾C原子的不饱和性,导致了甲基迁移产物和硅杂双环化合物的生成.     

H2Ge=Si:与甲醛生成含锗螺硅杂环化合物反应机理的从头算研究

用MP2/AUG-CC-PVDZ 方法研究了单重态H₂Ge=Si:与甲醛环加成反应的反应机理,该反应有一条主反应通道. 该反应所呈现的反应规律为：两反应物通过[2+2]环加成反应首先生成了一锗杂四元环硅烯,由于该锗杂四元环硅烯中Si:原子的3p空轨道与甲醛的π轨道形成了π→p授受键,使锗杂四元环硅进一步与甲醛结合生成了一中间体. 由于该中间体中的Si:原子在过渡态之后发生了sp³杂化,该中间体经过渡态异构化为含锗的螺硅杂环化合物. 该研究结果从理论上揭示了单重态H₂Ge=Si:及其衍生物(X₂Ge=Ge:, X=H, Me, F, Cl, Br, Ph, Ar, …)与非对称性π 键化合物环加成反应的反应机制.     

二甲基亚甲基硅烯与乙烯生成硅杂双环化合物反应机理的从头算研究

用CCSD(T)//MP2/6-31G^*方法研究了单重态二甲基亚烷基硅烯与乙烯生成硅杂双环化合物环加成反应的机理,根据该反应的势能面可以预言,该反应只有一条主反应通道. 该主反应通道所呈现的反应规律为：二甲基亚烷基硅烯中Si原子的3p空轨道与乙烯中的π轨道形成了π→p授受键,生成三元环中间体(INT1);扩环作用使INT1异构化为四元环硅烯(P2);P2中Si原子的sp³杂化使P2进一步与乙烯结合生成了硅杂双环化合物.     

亚锗基卡宾及取代亚锗基卡宾与环氧乙烷抽提反应机理的密度泛函理论研究

采用B3LYP/6-311G(d,p)方法研究了单重态亚锗基卡宾及取代亚锗基卡宾X₂Ge=C:(X=H, F, Cl, CH₃)与环氧乙烷的氧转移反应机理. 结果表明, 由于环氧乙烷中氧上的2p孤对电子向X₂Ge=C:中C上的2p空轨道迁移,形成了p→p授受键,从而生成了各中间体. 随着p→p授受键的不断加强(即C-O键的逐渐缩短),中间体经过渡态生成了抽提产物. 取代基的电负性是影响该类反应的主要因素,取代基的电负性越大,反应的活化能越小     

Theoretical Study on Mechanism of Cycloadditional Reaction Between Dichloro-Germylidene and Formaldehyde

用MP2/6-31G^*方法研究了单线态二氯亚甲基锗烯与甲醛环加成反应的反应机理,该反应有两条相互竞争的主反应通道,同时伴随着两中间体(INT3和INT4)副产物的生成. 第一条主反应通道所生成的物种为三员环中间体(INT1)和Ge-O顺位的四员环产物(P1);第二条主反应通道所生成的物种为Ge-O对位的扭曲四员环中间体(INT2)和氯迁移产物(P2);P1和INT2分别与甲醛(R2)的进一步作用而导致了两副产物的生成.     

用从头算方法研究GeCl2分子的非谐振力场和光谱常数

用从头算方法的MP2和CCSD（T）方法结合cc-pVTZ基组计算了二氯化锗同位素（⁷⁰GeCl₂、⁷²GeCl₂和⁷⁶GeCl₂）分子的平衡结构、光谱常数和非谐振力场.二氯化锗的几何结构、转动常数、振转相互作用常数、谐频、非谐振常数、四次和六次离心畸变常数、三次和四次力常数的计算结果与实验结果符合较好,二氯化锗分子的同位素效应较小,可能的原因是Ge同位素的质量变化相对较小.两种方法计算的结果均与实验结果符合,但CCSD（T）方法比MP2计算结果的偏差稍大一些,可能的原因是CCSD（T）方法在描述过共价Cl原子的电子相关时不够充分.     

几种咪唑-二氧杂环的含能取代衍生物的理论研究

使用DFT的B3LYP方法对几种咪唑二氧杂环化合物的分子结构、红外光谱、生成焓、爆轰性能和化学/热稳定性进行了研究.四种不同含能基团-NO₂,-NH₂,-N₃和-ONO₂对该化合物各项性能的影响进行了比较.结果表明-NO₂和-ONO₂基团有效地增加了化合物的密度,而-N³基团极大地增加了化合物的生成焓.其中-NO₂取代物爆轰性能接近1,3,5,7-tetranitro-1,3,5,7-tetraazacyclooctane,-ONO₂取代物的爆轰性能低于hexahydro-1,3,5-trinitro-1,3,5-triazine.自然键轨道分析表明,这些化合物中相对较弱的键为取代基和咪唑环之间的键,以及二氧杂环中的C-O键.吸电子基团(-NO₂, -N³和-ONO₂)在分子中产生了明显的诱导效应,减弱了基团与咪唑环之间的链接,降低了对应键的键裂解能.研究表明基团的电负性与化合物的稳定性有关.考虑到化合物的爆轰性能和热稳定性,DNTNDI化合物满足高能量密度材料的要求.     

时间切片离子速度成像技术关于MgO在193 nm的光解反应动力学研究

本文利用时间切片离子速度成像技术对MgO分子在193 nm下的光解反应动力学进行了研究. 实验通过产物Mg的速度和角度分布分析,发现了三个光解反应路径. 路径一为MgO(X¹Σ⁺)态分子吸收一个光子到MgO(G¹π) 态,由于G¹π, 3³π和1⁵π态之间的自旋轨道耦合作用,反应沿着1⁵π的势能面解离生成产物Mg(³P_u)+O(³P_g). 路径二、三分别为MgO(A¹π)态分子吸收一个光子到MgO(G¹π)态和MgO(4¹π) 态,进而解离生成产物Mg(³P_u)+O(³P_g)和Mg(¹S_g)+O(¹S_g). 光解离路径的各向异性参数与振动能级的寿命以及转动和振动自旋轨道态的耦合有关. 从总动能分析得到D₀(Mg-O)=21645±50 cm^-1.     

质子化corroles的结构和电子光谱的密度泛函理论研究

用电子密度泛函理论研究了N-质子化corrole(H₄Cor⁺)和meso位芳基取代质子化corroles(H₄TPC⁺、H₄TpFPC⁺和H₄TdCPC⁺)的几何构型、内消旋反应机理以及电子光谱. 结果表明,这些化合物均有两种稳定构型(势能面极小),一个为C₂对称性的S1(最稳定构型),另一为C₁对称性的S2,其中S1的能量比S2低约15.8～18.5 kJ/mol.S1和S2的corrole环都呈现明显的面外扭曲变形. 手性S1的两个对映异构体之间的转化是一个以S2为中间态的多步过程. 用TDDFT计算了它们的紫外可见电子吸收光谱和圆二色谱(ECD). 与H₄Cor⁺相比,H₄TPC⁺、H₄TpFPC⁺和H₄TdCPC⁺的紫外可见吸收都发生了明显红移,且它们的Q带都因芳基取代基与corrole环之间的π-π共轭而明显增强. 计算表明,质子化corrole的若干相邻电子跃迁的旋转强度符号相反,表明ECD谱可能是研究其电子跃迁的有用工具.     

Electrical property of HfOxNy-HfO2-HfOxNy sandwich-stack films

The effects of HfO_xN_y on the electrical property of HfO_xN_y-HfO₂-HfO_xN_y sandwich-stack (signed as SS) films were investigated. Excellent electrical performances were achieved in SS films, with a high dielectric constant of 16 and a low leakage current of ∼2 × 10⁻⁸ A/cm² at 1 MV/cm. Schottky (SK) emission and Frenkel-Poole (PF) emission are found to be the dominant mechanisms for the current conduction behavior. After a long time stress, the flat-band voltage shift in the SS film is much smaller than that in a pure HfO_xN_y film indicating fewer charge traps existed in the SS film. Based on the experiments, the new SS structure is more favorable for the improvement of electrical performances than a pure HfO_xN_y or HfO₂ structure.     

含铜铁电电容器SrRuO3/Pb(Zr0.4Ti0.6)O3/SrRuO3/Ni-Al/Cu/Ni-Al/SiO2/Si异质结的研究

应用磁控溅射法以Ni-Al同时作为Cu与SiO₂/Si,Cu与SRO薄膜之间的阻挡层材料,将Cu与SiO₂/Si衬底和氧化物薄膜电极隔离,避免它们在高温氧气氛中发生化学反应和互扩散,实现了Cu薄膜与氧化物铁电电容器的集成.采用X射线衍射仪(XRD)和原子力显微镜(AFM)研究了不同温度下快速退火的SrRuO₃(SRO)/Ni-Al/Cu/Ni-Al/SiO₂/Si含Cu异质结的微结构和表面形貌,结果发现SRO/Ni-Al/Cu/Ni-Al/SiO₂/Si含Cu多层异质结薄膜在高达750 ℃仍然具有较强的Cu衍射峰和比较平整的表面,显示出了很好的高温热稳定性.研究了"室温长高温退"和"低温长高温退"两种工艺手段,发现在制备含Cu多层氧化物薄膜异质结时,低温长高温后退火的方式要优于常规的室温长高温后退火方式,通过低温长高温退工艺可以缓解应力、削弱界面粗化和避免高温生长对阻挡层和Cu薄膜结构的破坏.最后结合sol-gel法将Pb(Zr_0.4Ti_0.6)O₃(PZT)生长在该含Cu异质结上,制备得SRO/PZT/SRO/Ni-Al/Cu/Ni-Al/SiO₂/Si含Cu铁电电容器,研究了电容器的薄膜结构、铁电性能和漏电特性等,发现制备的含Cu铁电电容器具有很好的铁电性能,如电滞回线趋势饱和,剩余极化强度高达~42 μC/cm²,矫顽电压为~1.0 V,介电常数~1600,漏电流~1.83×10^-4 A/cm²,以及良好的抗疲劳特性和保持特性等,表明导电性优良的Cu薄膜可以应用于高密度高性能铁电电容器.对其漏电机理研究表明,SRO/PZT/SRO含Cu铁电电容器满足空间电荷限制传导机理. 关键词： Cu PZT 铁电电容器 Ni-Al     

Elastic properties of the RIV-RIII rotator phases of alkanes

A model free energy has been constructed to describe the R_IV-R_III rotator phase transition in alkanes in terms of the elastic strains and order parameter. The conditions for the R_IV-R_III phase transition are discussed. From the free energy, the order parameter and the elastic strains are determined. The model free energy describes the first or second order character of the R_IV-R_III transition depending on the strength of the coupling. The elastic properties in the vicinity of the R_IV-R_III transition are discussed on the basis of a free energy expansion. The temperature dependence of the elastic constants is calculated on both sides of the transition. The coupling between the order parameter and elastic stains is shown to have a crucial influence on the phase behavior and the order of the transition.     

Magnetic properties of Fe1−xCoxO

Measurements are reported for the magnetic susceptibility of solid solutions Fe_1-xCo_xO for compositions with x =0.10 to 0.95 and for the temperature range 4.2 to 600 K. It is found that the Curie-Weiss law is obeyed at high temperatures while the dependence of the susceptibility and transition temperature on composition appear to be in good agreement with the “virtual crystal” approximation.     

Electronic and magnetic structures of V-doped zinc blende Zn1-xVxNyO1-y and Zn1-xVxPyO1-y

Electronic and magnetic structures of zinc blende ZnO doped with V impurities are studied by first-principles calculations based on the Korringa-Kohn-Rostoker (KKR) method combined with the coherent potential approximation (CPA).Calculations for the substitution of O by N or P are performed and the magnetic moment is found to be sensitive to the N or P content.Furthermore,the system exhibits a half-metallic band structure accompanied by the broadening of vanadium bands.The mechanism responsible for ferromagnetism is also discussed and the stability of the ferromagnetic state compared with that of the paramagnetic state is systematically investigated by calculating the total energy difference between them by using supercell method.     

Vibrational spectroscopy of Cm-C/Cb-Cb stretching vibrations of copper tetramesityl porphyrin: An algebraic approach

Using Lie algebraic techniques and simpler expressions of the matrix elements of Majorana and Casimir operators given by us, we obtain an effective Hamiltonian operator which conveniently describes stretching vibrations of biomolecules. For a copper tetramesityl porphyrin molecule, the higher excited vibrational levels are calculated by applying the U(2) algebraic approach.     

Different temperature dependence of carrier transport properties between AlxGa1-xN/InyGa1-yN/GaN and AlxGa1-xN/GaN heterostructures

The temperature dependence of carrier transport properties of AlxGa1-xN/InyGa1-yN/GaN and AlxGa1-xN/GaN heterostructures has been investigated.It is shown that the Hall mobility in Al0.25Ga0.75N/In0.03Ga0.97N/GaN heterostructures is higher than that in Al0.25Ga0.75N/GaN heterostructures at temperatures above 500 K,even the mobility in the former is much lower than that in the latter at 300 K.More importantly,the electron sheet density in Al0.25Ga0.75N/In0.03Ga0.97N/GaN heterostructures decreases slightly,whereas the electron sheet density in Al0.25Ga0.75N/GaN heterostructures gradually increases with increasing temperature above 500 K.It is believed that an electron depletion layer is formed due to the negative polarization charges at the InyGa1-yN/GaN heterointerface induced by the compressive strain in the InyGa1-yN channel,which e-ectively suppresses the parallel conductivity originating from the thermal excitation in the underlying GaN layer at high temperatures.     

Extension of Rydberg absorption series of N2, A 2Πu ← X 1Σg+

Rydberg absorption series of N₂ converging to the $\text{A}{}^2\text{Π}{}_{\mathrm{u}}$ state of N₂⁺ have been reinvestigated with a 6.65-m normal incidence vacuum spectrograph in the second order. Previously known A ← X series (I) and (II) have been extended to higher members with m ～ 40 and up to v′ = 7.     

碱金属Li,Na,K,Rb,Cs,Fr的ns2S1/2,np2P1/2,3/2, nd2D3/2,5/2 和nf2F5/2,7/2 里德伯能级理论研究

本文在多通道量子数亏损理论(MQDT)框架下,利用相对论多通道理论(RMCT),分别在冻结实近似、 考虑Δl=-1的偶极极化效应、Δl=+1的偶极极化效应、Δl=± 1的偶极极化效应、伸缩模效应以及同时考虑偶极极化效应和伸缩模效应等不同层次近似下,系统地计算了碱金属Li, Na, K, Rb, Cs和Fr七个里德伯系列的能级,即ns²S_1/2, np²P_1/2, np²P_3/2, nd²D_3/2, nd²D_5/2, nf²F_5/2 和nf²F_7/2.计算结果表明,电子关联效应对碱金属原子的里德伯能级的影响很大.总的来说,偶极极化效应比伸缩模效应重要,而在偶极极化效应中, Δl = + 1的偶极极化效应比Δl = - 1的偶极极化效应重要.但对于Na的ns²S_1/2,(nd²D_3/2,nd²D_5/2)里德伯系列的能级,和Li的(np²P_1/2,np²P_3/2)里德伯系列的能级,是伸缩模效应比较重要.     

Near-infrared bands of S2: 3Πgi-3Σu+ system

Vibrational and rotational analyses of the near-infrared bands of S₂ lying in the region 7440–8085 Å are reported. They form a new band system involving a ${}^3\text{Π}{}_{\mathrm{gi}}\text{-}{}^3\text{Σ}{}_{\mathrm{u}}{}^{\mathrm{+}}$ transition and arise from the same initial ³Π_gi state of the ³Π_gi-³Δ_ui band system reported earlier. The analyses of the bands of this system due to the isotopic molecules ³²S³⁴S and ³⁴S₂ are also reported.