Pu+4的几何构型和Jahn-Teller效应

在Pu原子的相对论有效原子实势下,用密度泛函B3LYP方法计算得到Pu +4分子离子的6种稳定的几何构型.计算表明Pu+4的Td构型不能稳定存在,详细讨论了 Td构型的Jahn-Teller效应,讨论结果显示它们的各种畸变方式都符合群的分解原理, 从而证明Pu+4分子离子的Td构型的Jahn-Teller效应非常明显.D4h 构型也存在Jahn-Teller效应.     

C2+4的几何构型和Jahn-Teller效应

用从头计算法GCISD/6-311G*得到了C2+4分子的10种不同的几何构型,基中包括Cs,C∞v,C2v,D2h,D∞h,D4h,D2d,C3v等不同的构型.计算表明C2+4的Td构型不能稳定存在,详细讲座了Td构型的Jahn-Teller效应.讨论结果显示它们的各种畸变方式都符合群的分解原理,从而证明了C2+4分子的Td构型的Jahn-Teller效应非常明显.D4构型也存在Jahn-Teller效应.     

C42+的几何构型和Jahn Teller效应

用从头计算法QCISD/6-311G得到了C₄²⁺分子的10种不同的几何构型,其中包括C_s,C_∞v,C_2v,D_2h,D_∞h,D_4h,D_2d,C_3v等不同的构型.计算表明C₄²⁺的T_d构型不能稳定存在,详细讨论了T_{d 关键词： 几何构型 4}²⁺')" href="#">C₄²⁺ Jahn Teller效应     

ZnSe∶Fe~(2+)中的动态Jahn-Teller效应和远红外光谱的研究

推导了 3d4 / 3d6离子基态 5D在立方晶体场、自旋 轨道耦合和动态Jahn Teller效应作用下的哈密顿矩阵 ,并用对角化该哈密顿矩阵的方法研究了Fe2 + 在ZnSe中的远红外光谱 ,理论计算与实验符合得好 .研究表明 ,在ZnSe∶Fe2 + 中 ,比晶体场理论分析多出的分裂谱线是Fe2 + 与ZnSe晶格间的动态Jahn Teller效应引起的 .还预测了其它Jahn Teller效应分裂谱 .所推导的哈密顿矩阵对研究 3d4 / 3d6离子在立方晶体中的精细光谱、电子顺磁共振谱和动态Jahn Teller分裂都是有用的 .     

Pu2+2 分子离子的结构与势能函数

使用密度泛函B3LYP方法对Pu2+2分子离子进行了理论研究,结果表明,Pu2+2分子离子是亚稳定结构,基态电子状态为 13Σg,势能函数可以用Z-W函数来表征,并首次计算获得基态分子离子的力常数和光谱数据.     

PuNn+分子离子的势能函数与稳定性

用密度泛函B3LYP方法对PuN^n+（n=1,2,3)分子离子进行了理论研究。结果表明：PuN^+、PuN^2＋分子离子能稳定存在,基态电子状态是X^5 ∑^+(PuN^+)和X^4∑^+(PuN^n+),并导出了相应的几何性质、力学性质和光谱数据。PuN^3+（^5∑、^7∑、^9∑）分子离子不能稳定存在。     

Pu_3体系的结构与势能函数

用相对论有效原子实势 (RECP)和密度泛函 (B3LYP)方法对Pun(n =2 ,3)体系的结构进行了优化 ,得到了Pu2 和Pu3分子的几何构型分别为D∞h,D3h,其基态分别为 13和 19重态 .在B3LYP RECP水平上得到Pu2 分子的光谱常数ωe=5 2 .3845cm- 1 ,ωe 　χe=0 .0 2 0 1cm- 1 和Pu3分子的谐振频率 (ν1 =5 6 .90 0 7cm- 1 ,ν2 =5 7.1816cm- 1 ,ν3=6 4 0 785cm- 1 )等性质 ,并通过正规方程组和多体展式理论 ,得到了Pu2 ,Pu3的分析势能函数 .     

利用快分子离子与固体的相互作用对H2+,HD+和D+2结构的研究

利用快分子离子与固体的相互作用,依靠一套高分辨装置,测量了H2+,HD+和D2+的结构,得到其核间距分别为1.19±0.003 nm、1.25±0.003 nm和1.32±0.003 nm.通过对比,证实了分子离子结构中同位素效应的存在,分析了实验值和理论值存在差别的原因,讨论了实验结果中同位素效应产生的缘由.     

NH4+离子的结构和振动光谱

用Gaussian 03W 程序中的密度泛函B3LYP/6-31+G(d)方法对氨分子的质子化产物NH4+离子的可能几何构型进行了结构优化和频率计算,得到了它的稳定结构和红外振动光谱. 通过对计算结果的分析发现,NH4+的稳定构型为正四面体结构,属Td分子点群;它的红外振动光谱中共有两个位于3390 cm-1和1478 cm-1处的三重简并振动峰,分别对应着N-H键的反对称伸缩振动和弯曲振动.     

PuCn+(n=1,2,3)分子离子的势能函数与稳定性

用密度泛函B3LYP方法对PuCn+(n=1,2,3)分子离子进行了理论研究,结果表明:PuC+、PuC2+分子离子能稳定存在,基态电子状态是X8Σ-(PuC+)和X9Σ-(PuC2+),并导出了相应的几何性质、力学性质和光谱数据.PuC3+(6Σ、8Σ)分子离子不能稳定存在.     

Multiple groups in the symmetry classification of adiabatic electronic wavefunctions

It was originally shown by Longuet-Higgins and colleagues that when the electronic Schrödinger equation is solved as a function of the nuclear coordinates the adiabatic electronic wavefunction can undergo a change of sign after completing a closed circuit. This geometric phase occurs for a circuit around a conical intersection, and in particular around a conical intersection corresponding to a linear Jahn—Teller effect. The adiabatic wavefunctions are classified here under a group called the adiabatic multiple group, which is a generalization of the ‘vibronic double group’ of C _3v introduced by Hougen, and is distinct from the familiar electron-spin double group. Although the real electronic wavefunctions can be only double-valued, the groups can have higher multiplicity because of the possibility of different circuits. For a number of symmetric- and spherical-top point groups, the adiabatic multiple group is shown to be the direct product of the point group with a phase group. The adiabatic multiple group can be applied to individual adiabatic orbitals, and so to configurations built from these orbitals. This leads to the rule that the linear Jahn—Teller effect vanishes in the single-configuration approximation for configurations containing non-degenerate electrons plus an even number of e electrons. There does not appear to be any cancellation effect for electron configurations of cubic molecules containing f electrons.     

CN~+离子电子结构和跃迁性质的理论研究

采用多组态参考相互作用方法和AV5Z-DK基组对CN~+离子的两个解离极限C~+(~2P_u)+N(~2D_u)和C~+(~2P_u)+N(~4S_u)下的X~1Σ~+、a~3Π、~1Δ和A~1四个电子态的势能曲线、永久偶极矩和振动能级进行了计算.为保证计算结果的精确性,在计算中考虑了Davidson修正.基于求得的势能曲线,数值求解一维径向薛定谔方程得到了各个电子态的光谱数据,并与实验值和已有的理论值吻合较好.除此之外,对A~1Π→X~1Σ~+和1~1Δ?A1~Π的跃迁性质进行了研究,同时通过跃迁的弗兰克-康登因子及辐射寿命,对CN~+离子激光冷却的可行性进行了分析.     

Electron spin resonance study of a CuIr2S4 single crystal

A spinel sulphide CuIr₂S₄ single crystal, which exhibits an orbitally induced Peierls phase transition at ～230?K, is investigated by electron spin resonance (ESR) spectroscopy. The phase transition is clearly manifested on the ESR spectra. It is suggested that the ESR signals are produced by a few non-dimerized Ir⁴⁺ ions. Moreover, an extra ESR spectrum appears at low temperature in addition to the paramagnetic ESR signals of Ir⁴⁺ ions, which is suggested to be caused by the Jahn–Teller effect of the non-dimerized Ir⁴⁺ ions. From the ESR results, it is found that the Jahn–Teller splitting energy ΔE _JT is much smaller than the spin-dimerization gap.     

A first-principles study on phase transition induced by charge ordering of Mn3+/Mn4+ in spinel LiMn2O4

A first-order transition at 290 K in LiMn₂O₄ with a cubic spinel-type structure is known to degrade the electrochemical performance of the positive electrode of rechargeable lithium-ion batteries. Using first-principles density functional theory (DFT), we confirm that the phase transition is induced by charge-ordering of Mn³⁺/Mn⁴⁺ accompanied by orbital-ordering due to Jahn–Teller distortion, which is in agreement with the previous experimental results of Rodríguez-Carvajal et al. [J. Rodríguez-Carvajal, G. Rousse, C. Masquelier, M. Hervieu, Phys. Rev. Lett. 81 (1998) 4660]. The optimized structure of the low-temperature (LT) phase has orthorhombic symmetry with five distinct crystallographic sites for Mn. The spin integration at each Mn site shows that Mn³⁺ resides at three Mn sites and the remaining two sites are occupied by Mn⁴⁺ ions. Total energy calculations indicate that the LT phase is about 0.23 eV/ LiMn₂O₄ more stable than cubic LiMn₂O₄ (high-temperature phase). The electrochemical Li extraction reaction from the LT phase is also investigated using DFT calculations. The results indicate that the reaction is initially divided into two voltage regions. Electrostatic interactions in the LT phase are calculated using a point charge model, accounting for the features of the electronic configurations and electrochemical reactions.     

Theory studies of the local lattice distortions and the EPR parameters for Cu2+, Mn2+ and Fe3+ centres in ZnWO4

The local lattice distortions and the electron paramagnetic resonance (EPR) parameters (g factors, hyperfine structure constants and zero-field splittings) for Cu²⁺, Mn²⁺ and Fe³⁺ in ZnWO₄ are theoretically studied based on the perturbation calculations for rhombically elongated octahedral 3d⁹ and 3d⁵ complexes. The impurity centres on Zn²⁺ sites undergo the local elongations of 0.01, 0.002 and 0.013 Å along the C₂ axis and the planar bond angle variations of 8.1°, 8.0° and 8.6° for Cu²⁺, Mn²⁺ and Fe³⁺, respectively, due to the Jahn–Teller effect and size and charge mismatch. In contrast to the host Zn²⁺ site with obvious axial elongation (～0.31 Å) and perpendicular (angular) rhombic distortion, all the impurity centres demonstrate more regular octahedral due to the above local lattice distortions. The copper centre exhibits significant Jahn–Teller reductions for the spin-orbit coupling and orbital angular momentum interactions, characterised by the Jahn–Teller reduction factor J (≈0.29 ? 1). The calculated EPR parameters agree well with the experimental results. The local structures of the impurity centres are analysed in view of the corresponding lattice distortions.     

Structural,Magnetic and Optical Properties of Rh2☎ Centres in NaCl Lattices: An Explanation

A method for exploring Jahn—Teller systems in the framework of Density Functional Theory is described in the present work. Using such a method the properties of the Rh^2? centre in NaCl with remote charge compensation are studied. The calculations support the existence of a strong Jahn—Teller effect and account reasonably for the main features of EPR and optical spectra. The onset of charge transfer excitations is calculated to be at about 3.7 eV a fact which concurs with available experimental data. The elongated geometry is found to be about 200cm^?1 more stable than the compressed one in agreement with experiments.     

Contribution from structural Jahn–Teller ions to the elastic and ferroelectric properties of lithium niobate and lithium tantalate

Elastic and ferroelectric characteristics of single crystals of lithium niobate and tantalate are investigated in a wide range of temperatures by complex acoustooptic means. The contribution from Jahn–Teller NbO₆ and TaO₆ systems to the characteristics of elastic moduli, ultrasonic attenuation, and nonlinear optical coefficients is analyzed using a new phenomenological model. It is hypothesized that the displacement of Nb⁵⁺ and Ta⁵⁺ ions, which exhibit the second-order Jahn–Teller effect along trigonal axis C, and the subsequent ordering of octahedral, result in unusual elastic and ferroelectric properties.