VH_2~+分子离子的结构与势能函数

本文从VH2+分子离子基态的电子状态及其离解极限出发,采用B3PW91的方法,对V原子采用SVP基组,对H原子采用6-311 ++G基组优化出VH2+(X3A2)分子离子稳定构型的平衡核间距Re=0 .1631 nm,∠HVH =112 .3858°,同时计算出振动频率,并使用多体项展式理论方法,导出了基态VH2+分子离子的分析势能函数,该势能表面准确地再现了VH2+(C2v)平衡结构,然后根据势能函数等值图讨论了反应势能面的静态特征,并利用杂化轨道理论解释了VH2+分子离子的结构.     

MC与M_(n+1)AC_n稳定性与电子特征的第一性原理研究

研究M C与M n+1A C n(M=Sc,Ti,V,Cr,Mn;A=Al,Si,P,S;n=1,2,3)结构的稳定性与电子特征有利于探究三元层状结构M n+1A C n稳定性的内在原因和设计新型M n+1A C n结构.第一性原理计算研究表明,M-3d与C-2p轨道间的电子转移对M C与M n+1A C n的形成焓有较大影响.供电子能力较强的前过渡金属可以形成稳定的M C结构.计算结果显示,M C结构是缺电子体系,其趋向于与具有一定供电子能力的MA结构结合形成M n+1A C n.与M2PC和M2SC相比,M2Al C和M2Si C可以更为容易地被分离成二维M2C结构.     

VH2+分子离子的结构与势能函数

本文从VH2 分子离子基态的电子状态及其离解极限出发,采用B3PW91的方法,对V原子采用SVP基组,对H原子采用6-311 G基组优化出VH2 (X3A2)分子离子稳定构型的平衡核间距Re=0 .1631 nm,∠HVH =112 .3858°,同时计算出振动频率,并使用多体项展式理论方法,导出了基态VH2 分子离子的分析势能函数,该势能表面准确地再现了VH2 (C2v)平衡结构,然后根据势能函数等值图讨论了反应势能面的静态特征,并利用杂化轨道理论解释了VH2 分子离子的结构.     

(HgSe)_n(n=1～6)团簇结构和性质的密度泛函研究

本工作采用LANL2DZ赝势基组、B3LYP方法对(HgSe)n(n=1~6)团簇进行了结构优化、自然键原子轨道和频率计算,得到(HgSe)n(n=1~6)团簇基态的平衡几何结构、电子状态、垂直电离势、垂直电子亲和势、偶极矩、三个基本热力学函数等相关性质,并系统分析了该团簇的几何构型、原子净电荷布局、前沿分子轨道特征.结果表明:基态稳定结构(HgSe)2为平面四边形,(HgSe)n(n=3~6)为笼状结构,且稳定顺序为(HgSe)5(HgSe)4(HgSe)6(HgSe)2HgSe(HgSe)3,极性顺序为:(HgSe)4HgSe(HgSe)3(HgSe)5(HgSe)6(HgSe)2,(HgSe)6和(HgSe)2分子空间结构的对称性较好.(HgSe)n(n=1~6)团簇各体系都有较好的电子供体及受体等活性部位,随着n增大轨道离域现象明显,利于电子的转移,导电性增强.     

563—660nm波段S02^＋的PHOFEX连续谱

在超声分子束条件下，利用380．85nm的电离激光使SO2分子经由[3+1]共振增强多光子电离(REM—PI)产生纯净的S02^+(X^2A1)分子离子，用另一束解离激光在可见光波长区(563—660nm)扫描获得了光解碎片S0^+的激发(PHOFEX)谱．从563—66nm波长区SO^+的无结构连续谱以及S02^+解离的效率随波长增加而减少的实验事实，提供了S02^+(E，D，C)电子态附近存在α^2A2对称性排斥态的证据，分析了产生S0^+的[1+1]光解机理：(1)S02^+(X^2A1)首先经由单光子激发到达B^2B2中间态的密集能级区；(2)吸收另一个光子到达S02^+(E，D，C)电子态附近的α^2A2排斥态，经由α^2A2排斥态产生了到S0^+(X^2∏)+O(^3P6)的直接解离．     

腺嘌呤-5-溴尿嘧啶复合物中的卤键

利用从头算和密度泛函理论研究了腺嘌呤(A)-5-溴尿嘧啶复合物中(T+)中的键合模式. 研究结果表明，T+中的Br原子同时与A分子中的氨基氢和氮原子存在弱的相互作用，在这种结合模式中，Br原子与亲核基团H正面结合，同时与亲电基团N侧面结合，分别形成氢键和卤键.静电势分析发现：T+中的Br原子与A中的N7 (或N1)是通过静电相互吸引的. Br与N原子之间的相互作用通过分子中的原子理论得以证实. 关键点的拓扑参数显示卤键是闭壳层相互作用. 自然键轨道分析说明，A中N原子上孤对电子的电荷主要转移到C{Br的反     

M2Al2(M=Au,Ag,Cu)混合小团簇的密度泛函研究

采用基于密度泛函理论的B3LYP方法,利用小核实赝势LANL2DZ,优化了含重金属二元混合团簇M2Al2(M=Au,Ag,Cu)的稳定结构,并得出具有C2v(1A1)对称性的蝴蝶结构比平面构型更加稳定,其中团簇Au2Al2最稳定.计算了稳定结构的结合能、电离势、电子亲和能、最高占据轨道能级和最低空轨道能级及二者间的能隙,得出参杂团簇M2Al2比非参杂团簇M4(M=Au,Ag,Cu)更稳定的结论.     

(HgSe)n(n=1~6)团簇结构和性质的密度泛函研究

本工作采用LANL2DZ赝势基组、B3LYP方法对(HgSe)n(n=1~6)团簇进行了结构优化、自然键原子轨道和频率计算,得到(HgSe)n(n=1~6)团簇基态的平衡几何结构、电子状态、垂直电离势、垂直电子亲和势、偶极矩、三个基本热力学函数等相关性质,并系统分析了该团簇的几何构型、原子的净电荷布局、前沿分子轨道特征。结果表明：基态稳定结构(HgSe)2为平面四边形,(HgSe)n(n=3~6)为笼状结构,且稳定顺序为(HgSe)5>(HgSe)4>(HgSe)6>(HgSe)2>HgSe>(HgSe)3,极性顺序为：(HgSe)4>HgSe>(HgSe)3>(HgSe)5>(HgSe)6>(HgSe)2,(HgSe)6、(HgSe)2分子空间结构的对称性较好。(HgSe)n(n=1~6)团簇各体系都有较好的电子供体及受体等活性部位,随着n增大轨道离域现象明显,利于电子的转移,导电性增强。     

胸腺嘧啶-BH3构型与性质的DFT和MP2研究

对胸腺嘧啶 BH3复合物分别用B3LYP/6 31G(d)和MP2/6 31G(d)进行计算,以预测该复合物的构型 及结合能,得到了5种构型,并进行了振动分析和自然键轨道分析.对各构型进行了更大基组(6 311+G(2df)和 aug cc pVDZ)的单点能量计算.结果表明,B原子与O原子直接相连的构型(a)、(b)比较稳定,其结合能为90.4 和88.0kJ/mol(B3LYP/6 31G(d),BSSE校正).N原子向B原子的空轨道提供电子形成构型(c)和(d),只找到 了一种由C原子向B原子提供π电子的构型(e).所有构型中均存在电荷授受,各构型的结合能与电荷转移量有 良好的相关性.复合物的形成,使其红外光谱均有不同程度的红移,红移幅度与复合物的稳定性相关.     

1,1-二氨基二硝基乙烯晶体的密度泛函理论研究

对 1,1 二氨基二硝基乙烯晶体进行了DFT B3LYP水平计算 .计算所得晶格能为 -10 5 .81kJ/mol,与文献值相近 .晶体的前线能带较为平坦 ,表明分子轨道能态受分子晶体场的影响较小 .电荷的分布决定了晶体中DADNE以“头 尾”方式通过分子间氢键相连形成层状结构 ,而层与层之间相互作用较弱 .从带隙 4.0eV推知DADNE的导电性介于半导体和绝缘体之间 .前线轨道由C -NO2 的原子轨道所组成 ,说明分子的强共轭性 ,也表明C -NO2 为化学反应活性部位 .C -NO2 键的布居数远小于其它键 ,提示该键为起爆引发键     

Quantum chemical studies on a series of transition metal carbon dioxide complexes: Metal–carbon bonding and electronic structures

The bonding features and electronic structures of a series of transition metal carbon dioxide complexes have been studied by density functional theory (DFT) calculations combined with natural bond orbital (NBO) analysis and energy-decomposition analysis (EDA). NBO analysis shows that the interaction between the metal center and the carbon atom of the carbon dioxide ligand (M–C) is stronger than the other interaction between the metal center and the carbon dioxide ligand. Natural hybrid orbital (NHO) analysis gives the detailed bonding features of the M–C bond for each complex. The NBO charge distribution on the carbon dioxide unit in all studied complexes is negative, which indicates charge transfer from the metal center to the carbon dioxide ligand for all studied complexes. The hyperconjugation effect of the metal center and the two C–O bonds of the carbon dioxide ligand has been estimated using the NBO second-order perturbation stabilization energy. It was found that the NBO second-order stabilization energy of C–O?→?nM* is sensitive to the coordinated sphere and the metal center. Frontier molecular orbital (FMO) analysis shows that complexes 1 and 4 may be good nucleophilic reagents for activation of the carbon dioxide molecule. However, the EDAs show that the M–CO₂ bond interaction energy of complex 4 is about two times as large as that of complex 1. The high M–CO₂ bond interaction energy of complex 4 may limit its practical application.     

Chemical bonding and lithium ion conductions in Li3N

Electronic states of Li ions during the ionic jumps in the Li₃N crystal was discussed on the basis of the first principle molecular orbital calculations. The movements of the Li ions were simulated by several model clusters with different positions of the moving cation. The net charge of the moving Li ion and the total bond overlap population between the moving Li ion and the other ions were used for discussion of chemical bonding of the moving Li ion. Furthermore we have estimated the local cluster energy (LCE) to compare the energy change in the different moving path of the Li ion. The total bond overlap population of the moving Li ion along the conduction path changed smaller than those of the other paths. On the other hand, the changes of the net charges of the moving Li ions were similar in any paths. The change of the LCE in the model cluster of the conduction path was much smaller than that in another model cluster. As the results, the smaller change of the total bond overlap population of the moving Li ions played an important role for the fast ion movement in the Li ion conductors, rather than the change of the net charge of the moving Li ions. This bonding state of the moving Li ions is one of the characteristics of the electronic state in Li ion conductors.     

pr3+ 激活的CaMoO4红色荧光粉的发光性质

采用高温固相法制备了稀土pr3+激活的Ca1-xPrxMoO4(0.005≤x≤0.02)系列红色荧光粉.荧光光谱表明:在453 nm激发下,样品产生了红光发射,其中对应于pr3+的特征跃迁3 P0→3F2位于654 nm的红色发射峰最强.分析了pr3的掺杂摩尔分数x对样品发光强度的影响,确定pr3+的最佳掺杂摩尔分数...     

二亚胺混配镍(Ⅱ),铜(Ⅱ),锌(Ⅱ)配合物的电子光谱与感光氧化特性

报道了新近合成的马来腈二硫纶·5-硝基-邻菲咯啉混配镍(Ⅱ)、铜(Ⅱ)、锌(Ⅱ)配合物MLL’(L=mnt~(2-),1,2-二氰基乙烯-1,2-二硫醇离子,L’-5-NO_2-Phen,5-硝基-1,10-邻菲咯啉)在二甲基亚砜(DMSO),二甲基甲酰胺(DMF),乙二醇二甲醚(DME),乙醇(C_2H_5OH),四氢呋喃(THF),乙腈(CH_3CN)和二氯甲烷(CH_2Cl_2)中的电子吸收光谱,研究了电子光谱吸收带在相关分子轨道能级图中的对应跃迁关系,讨论了标题配合物有价值的配体间荷移跃迁(LL’CT)吸收带的本质特征及其影响因素,探讨了它们在DMSO中的感光氧化特性。     

C-H 键和C-C 键核自旋偶合常数的理论研究

利用PM3级别最大重迭对称性分子轨道法和最大键级杂化轨道方法,计算了系列烃类化合物的杂化轨道和电荷分布,拟合出计算C-H及C-C偶合常数的简单关系式. 研究了各种烃类分子中不同的C-H键和C-C键偶合常数,理论计算值和实验数据都较为符合. 进一步验证了直接键连¹J_CX偶合常数主要取决于偶合作用中的Fermi接触项,为从简单价键理论角度解释和计算¹J_CH和¹J_CC提供了一种简便直观的方法.     

Scaled Quantum Chemical Studies of the Molecular Structure and Vibrational Spectra of Minoxidil

The Fourier transform Raman and Fourier transform infrared spectra for minoxidil have been recorded in the region 4000—100 cm^?1 and 4000—450 cm^?1, respectively. The structural and spectroscopy data of the molecule in the ground state were calculated by using density functional theory methods with 6-311G (d, p) basis set. A detailed vibrational analysis of the title compound has been done using normal coordinate analysis following the scaled quantum mechanical force field methodology. The calculated molecular geometry parameters and scaled vibrational wavenumbers are well compared with the experimental data. The electronic properties, such as excitation energies, absorption wavelength, highest occupied molecular orbital (HOMO), and lowest unoccupied molecular orbital (LUMO) energies were performed by time-dependent density functional theory approach, and the results are in good agreement with experimental absorption spectrum. The charge delocalizations of these molecules have been analyzed using natural bond orbital analysis. The molecule orbital contributions are studied by density of energy states. Fukui functions, local softness, and electrophilicity indices for selected atomic sites of the title compound are determined. Finally, the thermal behaviors of the compound have been calculated by different temperature.     

外电场下GaN的特性研究

以6-311G(3df,3pd)为基组,采用B3PW91方法优化得到GaN基态分子的几何结构,并探究了电场对GaN分子基态能量、电荷布居数、键长、偶极矩、振动频率、红外光谱强度、HOMO、LUMO能级影响.研究表明:无电场时,谐振频率值为576.2218 cm~(-1),与实验值484.9 cm~(-1)很接近.有电场时,键长、偶极矩、能隙Eg、电荷布居数、红外谱强度、HOMO和LUMO能级随电场的增大而减小;谐振频率和分子总能量随电场的增加而增加.谐振频率和红外谱强度对电场有着明显的依赖关系,这对材料的光学特性研究有提供理论参考.     

Electronic structures of hydrogen in perovskite-type oxide,SrTiO3

The electronic structures of hydrogen in SrTiO₃ are simulated by the DV-Xα molecular orbital method. In pure SrTiO₃, there is a band gap of about 3.5 eV between the O-2p valence band and the Ti-3d conduction band, in agreement with experiments. When Sc is doped into SrTiO₃, an acceptor level appears just above the valence band. On the other hand, when hydrogen is introduced into SrTiO₃, a donor level appears below the conduction band. The molecular orbital of the donor level is composed mostly of the Ti-3d and O-2p electrons, but still there is a small occupancy (6%∼12%) of the H-1s electrons in it. When both Sc and hydrogen coexist in SrTiO₃, charge transfer takes place from the donor level to the acceptor level. As a result of this charge compensation, the effective ionicity of hydrogen becomes about +0.17∼+0.24, the value of which is dependent on the hydrogen positions in the crystal lattice. Also, the chemical bond strengths between constituent ions are modified largely by dopants. For example, the Sc doping tends to strengthen the chemical bond between hydrogen and oxygen ions, but instead to weaken the chemical bond between the oxygen ion and the surrounding metal ions. In addition, it is shown that an oxygen ion vacancy makes the defect level below the conduction band in the Sc-doped oxide.     

A Theoretical Study on <Emphasis Type="Italic">N</Emphasis>′-[(<Emphasis Type="Italic">Z</Emphasis>)-(4-Methylphenyl)Methylidene]-4-Nitrobenzohydrazide (NMPMN)

Quantum mechanical calculations of ground state energy, vibration wavenumbers, and electronic absorption wavelengths of N′-[(Z)-(4-methylphenyl)methylidene]-4-nitrobenzohydrazide with C15H13N3O3 empirical formula was performed by using Gaussian 09 program. Becke’s three-parameter exchange functional in conjunction with the Lee-Yang-Parr correlation functional and Heyd-Scuseria-Ernzerhof functional levels of density functional theory (DFT) with the 6-311++G(d,p) basis set were used in the performing of above mentioned calculations. The highest occupied and lowest unoccupied molecular orbital (HOMO and LUMO) energies have been also calculated at the same levels. Stability of the molecule arising from hyperconjugative interactions and charge delocalization has been analyzed using natural bond orbital (NBO) analysis. Nonlinear optical (NLO) behavior of the title molecule has been examined by the determining of electric dipole moment (μ), polarizability (α), and static first-order hyperpolarizability (β). Finally, molecular electrostatic potential (MEP) surface as well as Mulliken and NBO atomic charges were calculated by using Gaussian 09 program.     

Antiferromagnetic d-electron exchange via a spin-singlet pi-electron ground state in an organic conductor

Electron spin resonance reveals the spin behavior of conduction (pi) and localized (d) electrons in beta-(BDA-TTP)2MCl4 (M=Fe, Ga). Both the Ga3+(S=0) and Fe3+(S=5/2) compounds exhibit a metal-insulator transition at 113 K with the simultaneous formation of a spin-singlet ground state in the pi electron system of the donor molecules. The behavior is consistent with charge ordering in beta-(BDA-TTP)2MCl4 at the metal-insulator transition. At 5 K, the Fe3+ compound orders antiferromagnetically, even though the pi electrons, which normally would facilitate magnetic exchange, are localized nonmagnetic singlets.