非金属二元氢化物pka与量子化学参数的关系

在HF／3－21G水平下，对13种非金属二元氢化物分子（HF，HCl,HBr,HI,H2O,H2S,H2Se,H2Te,NH3,PH3,AsH3,CH4和SiH4)进行了几何构型全优化和电子结构计算，将获得的电子结构数据与这些分子的pka值相关联，进行逐步回归分析，结果显示，pka与非氢原子的键价，分子的最低空轨道能间存在显的二元线性相关性，相关系数R＝0．994。pka计算值与实验值符合得较好，表明非金属二元氢化物中非氢原子的键价，分子的最低空轨道能在决定其酸性上起重要作用。     

PdH2、YH2分子的结构与势能函数

用密度泛函理论的B3LYP方法,对钯和钇原子采用SDD收缩价基函数,氢原子采用6-311＋＋G**全电子基函数,对PdH2和YH2体系的结构进行优化计算,得到PdH2分子最稳态为C2v构型,电子组态为1A1,平衡核间距RPdH=0.1692 nm,键角∠HPdH=29.4°,离解能De=5.5212 eV,基态简正振动频率:ν1(b2)=1470.1 cm－1、ν2(a1)=1007.9 cm－1、ν3(a1)=2907.0 cm－1.YH2分子最稳态也为C2v构型,电子组态2A1,RYH=0.1962 nm,∠HYH=114.3°,De=5.6691 eV,基态简正振动频率:ν1(b2)=1457.9 cm－1、ν2(a1)=476.0 cm－1、ν3(a1)=1506.3 cm－1.由微观过程的可逆性原理分析了分子的可能离解极限.并用多体项展式理论方法分别导出基态PdH2和YH2分子的势能函数,其等值势能面图准确地再现了PdH2和YH2分子的结构特征和离解能,由此讨论了Pd ＋ H2和Y ＋ H2分子反应的势能面静态特征.     

Li_2H分子电子基态的从头算势能面及其振动激发态

用ab initio MRSDCI/6-311G(2 df,2 Pd)方法研究了Li_2H分子电子基态的势能面,计算了285个几何构型点的势能值,并采用Simons-Parr-Finlan展开式对这些势能值进行了拟合,得到均方差X~2等于4.64×10~(-6)(hartree~2).Li_2H分子电子基态的平衡几何构型为R_e=0.172nm,相似文献   

对取代苯Ph一X（X＝F，OH，NH_2）的价键理论研究

采用键表酉群方法对Ｃ６Ｈ５Ｆ、Ｃ６Ｈ５ＯＨ和Ｃ６Ｈ５ＮＨ２中的电子离域现象进行了计算和分析，讨论了取代苯的价键描述特性，并计算了取代基的π电子离域能．结果表明离子结构成分与离域能有直接关系，即离子成分越多，电子离域能越大．／６－３１Ｇ基组及“分子中的原子”方法将电荷密度分区积分得到各原子上的电荷集居数，并将此结果与取代苯的反应性能进行了比较。为在价键意义上分析和理解取代基对苯环电子结构及其反应性能的影响，本文对３个典型的取代苯Ｐｈ－Ｘ（Ｘ＝Ｆ，ＯＨ，ＮＨ２）进行了初步的价键计算和讨论．１计算方法及构型在键表酉群方法中［５］，体系的一个共振结构可用一个价键结构函数即键表ψ（ｋ）来描述，相应的体系总波函数Ψ可表示为Ｍ个正则键表的线性组合：式（１）便构成了键表相互作用（ＢＴＩ）计算方法［６］的基础．键表对体系的结构贡献定义为：原子轨道ｑ上的电荷集居数定义为：式中ｍｑ（ｋ）可取０、１或２，分别对应于键表ψ（ｋ）中原子轨道ｑ出现０、１或２次．为简比计算，我们将取代苯的σ骨架用ＨＦ分子轨道固定［７］，这样仅需考虑π电子及轨道．原子轨道积分及ＨＦ－ＳＣＦ计算采用Ｇａｕｓｓｉａｎ８０程序．联系人及第一作者：莫亦荣，男，２９     

PuC和PuC2的分子结构与势能函数

采用密度泛函B3LYP方法和相对论有效原子实理论模型优化出PuC和PuC2分子稳定构型,其电子状态分别为X5Σ－和X5A2.PuC2分子为C2v构型,其∠CPuC=147.67°,平衡核间距Re=0.22819 nm, 离解能De=5.543 eV, 并计算出谐振动频率:ν1=61.736 cm－1、ν2=229.894 cm－1、ν3=305.582 cm－1.在此基础上,运用多体项展式理论方法,导出了基态PuC2分子的分析势能函数,该势能面准确地再现了PuC2分子的稳定结构,并根据势能面等值图讨论了PuC＋C反应和Pu＋C2反应的势能面静态特征.     

等电子分子周期系

在无机化学教学中,人们常用等电子原理或价层电子对互斥理论来验证和预测一个分子及离子的空间构型。　　等电子原理常用于分子或离子空间构型的比较和判断。如N2中的N原子间以三键结合,那末与其等电子的CO分子中也有三键;ClO-4 为正四面体构型,同样SO2-4 也为正四面体构型。该理论虽有分子轨道理论为依托,但由于等电子族的数目是不可穷尽的,人们一般认为这些等电子族中只有少数可用作化学教学和结构研究的辅助工具。　　价层电子对互斥理论则用中心原子的价层电子数来判断分子或离子的空间构型。尽管多数人认为它是一个经验规则,但…     

Theoretical Investigation of LaC~n and La_2C~n(n=-1,0,+1)Clusters

用密度泛函方法研究了ＬａＣｎ及Ｌａ２Ｃｎ（ｎ＝－１，０，＋１）分子簇的结构和稳定性．对Ｌａ２Ｃｎ体系，提出了两种可能构型，其中一种具有Ｃ２ｖ对称性，另一种具有Ｄ∞ｈ对称性．计算结果表明，对Ｌａ２Ｃｎ，当ｎ＝＋１，－１时，线状结构最稳定，并且在ｎ＝＋１时，Ｃ２ｖ结构极不稳定有收敛向线状结构的趋势．而当ｎ＝０时，Ｃ２ｖ结构最稳定．最后还计算了ＬａＣ和Ｌａ２Ｃ分子簇的电子亲和势和离化能．     

螺旋共轭分子2，2‘—螺二茚—1，1’,3,3‘—四酮及其衍生物的二阶非线性光学性质与分子结构关系的研究

采用AM1和ZINDO系列方法研究了螺旋共轭分子2，2‘-螺二茚－1，1‘,3,3‘-四酮及其含氮衍生物的几何构型和各分子的稳定构型，并以稳定构型为基础，计算了这些分子的电子光谱、二阶非线性光学系数βμ，β0为电荷转移，考察了取代堪变化对βμ的影响。计算结果表明，所设计分子兼具较大的二阶非线性光学系数和较高的透过率，有希望成为一类新型的二阶非线性光学材料。     

丙烷分子的价轨道(2b2)电子的动量分布测量

电子动量谱学（EMS）是在原子、分子和固体物理中研究电子结构的一种强有力的工具，它基于运动学条件完全确定的（e，2e）碰撞电离反应[1-3]．本文报告用高分辨电子动量谱仪首次测量得到丙烷门3H8）分子的价轨道电子（252）的动量分布·丙烷（C3Hs）价轨道电子的动量分布实验是     

光异构化反应速率的量子理论

光异构化反应是在光场存在下，分子吸收光子引起的单分子化学反应，包括通常的异构化与环合、开环反应．一些作者用量子化学方法及分子轨道相关图和态相关图等方法对这类反应进行过研究［1］．本文用多声子光跃迁理论［2］研究光异构化反应，导出反应速率及其在低温条件下的解析表达式，对所得结果进行了讨论．1理论方法与结果在光异构化反应中，分子的电子状态与构型都发生变化，而且电子态的变化是与构型的改变紧密耦合的．分子的构型用分子的振动波函数来描写．由于电子与原子质量相差悬殊，可以采用绝热近似处理这一电子－振动相互作用…     

The Beijing four-component density functional program package (BDF) and its application to EuO, EuS, YbO and YbS

A four-component density functional program package (Beijing Density Functional), suitable for the calculation of total-energy-related chemical properties of systems containing heavy atoms, was developed. The code is based on modern sophisticated exchange-correlation functionals and was applied to calculate the spectroscopic constants of the lanthanide diatomic molecules of EuO, EuS, YbO and YbS. It is suggested that the experimental bond lengths for EuS and YbS, derived from empirical interpolations, need to be revised. Relativistic effects on the electronic structure are discussed and compared with results from previous work. The involvement of the lanthanide valence orbitals in chemical bonding is investigated with a newly developed population and bonding analysis approach. Received: 11 November 1996 / Accepted: 5 March 1997     

Synthesis and crystal structure determination of a new misfit compound: [(EuS)1.5]1.15NbS2

The crystal structure of the new misfit compound [(EuS)_1.5]_1.15NbS₂ has been determined via the composite approach. The structure is built up from three [EuS] layers (= slab noted ‘Q’) alternating with the [NbS₂] sandwich (= slab noted ‘H’) along the stacking direction (c axis). The cell parameters (Å) of this composite structure are: Q-part, a = 5.760(1), b = 5.780(1), c = 29.734(5); H-part, a = 3.317(1), b = 5.790(1), c = 14.859(4). Eu atoms located on the exterior sides of the Q-part show a quite regular hemi-octahedral coordination, whilst the inner Eu atoms show a distorted octahedral coordination. From bond valence calculations, one can assume that the outer Eu atoms are at the +II oxidation state and the inner Eu atoms at the +III state. The structure of the H-part appears very comparable to that found for other misfit compounds, i.e., Nb atoms in a trigonal prismatic coordination with S atoms, as for the binary NbS₂ itself.     

Synthesis and photophysical properties of EuS nanoparticles from the thermal reduction of novel Eu(III) complex

EuS nanoparticles were synthesized by the thermal reduction of single source precursor (SSP), (PPh4)[Eu(S2CNEt2)4].2H2O, under microwave irradiation. The average size of the EuS nanoparticles was found to be 8 nm (3-16 nm in size). The organic products on the EuS surface were observed by using FT-IR, NMR, and MS analyses. We have found that these are resulted from the chemical reactions of SSP and cover the nanocrystal surface. A thermal reaction of SSP gave EuS nanoparticles and the organic product (*SCN(Et)2). The organic product would make a dimmer, (Et)2NC(S)-(S)CN(Et)2, by the couping of the radicals formed in the thermal reaction and/or thiopolymer in the solution through the polymerization of the radicals. The effective surface modification by the organic products led to protection of the EuS surface, resulting in the formation of the strongly luminescent EuS nanoparticles at room temperature (emission peak = 350 nm, fwhm = 58 nm, emission quantum yield = 27 +/- 5%).     

Probing the electronic structure and chemical bonding of gold oxides and sulfides in AuOn(-) and AuSn(-) (n = 1, 2)

The Au-O and Au-S interactions are essential in nanogold catalysis and nanotechnology, for which monogold oxide and sulfide clusters serve as the simplest molecular models. We report a combined photoelectron spectroscopy and ab initio study on AuO (-) and AuO 2 (-) and their valent isoelectronic AuS (-) and AuS 2 (-) species to probe their electronic structure and to elucidate the Au-O and Au-S chemical bonding. Vibrationally resolved spectra were obtained at different photon energies, providing a wealth of electronic structure information for each species. Similar spectra were observed for AuO (-) and AuS (-) and for the linear OAuO (-) and SAuS (-) species. A bent isomer was also observed as Au(S 2) (-) in the AuS 2 (-) spectra, whereas a similar Au(O 2) (-) complex was not observed in the case of AuO 2 (-). High-level ab initio calculations were conducted to aid spectral assignments and provide insight into the chemical bonding in the AuX (-) and AuX 2 (-) molecules. Excellent agreement is achieved between the calculated electronic excitations and the observed spectra. Configuration interactions and spin-orbit couplings were shown to be important and were necessary to achieve good agreement between theory and experiment. Strong covalent bonding was found in both the AuX (-) and the XAuX (-) species with multiple bonding characters. While Au(S 2) (-) was found to be a low-lying isomer with a significant binding energy, Au(O 2) (-) was shown to be unbound consistent with the experimental observation. The latter is understood in the context of the size-dependent reactivity of Au n (-) clusters with O 2.     

一个二核钒配合物的合成及晶体结构：NH4[(VⅣO)2(μ2-O)(nta)2][EuⅢ(H2O)9](英)

A binuclear vanadium complex NH₄[(V^ⅣO)₂(μ₂-O)(nta)₂][Eu^Ⅲ(H₂O)₉] was synthesized by reaction of NH₃VO₃, nitrilotriacetic acid and EuCl₃ in one aqueous solution. The crystal X-ray analysis shows that the complex contains one binuclear vanadium anion [(V^ⅣO)₂(μ₂-O)(nta)2]^4- and one [Eu^Ⅲ(H₂O)₉]³⁺ cation. The molecules are built up to a three-dimensional supramolecular structure through hydrogen bonding. CCDC: 238716.     

A novel method for synthesizing EuS nanocrystals from a single-source precursor under white LED irradiation

EuS nanocrystals, with an average diameter of 9 nm, have been synthesized by the photolysis of Na[Eu(S2CEt2)4].3.5H2O; the first quantum confined particles of EuS to be reported.     

Local orbital study of bonding in small rings: Cyclopropane,thiirane, oxirane,and aziridine

The nature of the bonding in the three-membered ring molecules cyclopropane, thiirane, oxirane, and aziridine has been investigated throughab initio FSGO calculations. The direct correspondence between floating spherical Gaussian orbitals and specific chemical bonds has been used to study the degree of “bond bending”. In accord with chemical intuition, it is demonstrated that the C-C ring bond becomes progressively more bent as the bond length is reduced. C-C bonds are found to be more flexible than C-N (O, S) bonds. The sizes and locations of carbon-heteroatom bond orbitals and C-H bond orbitals are also discussed.     

Adsorption of N2O on Cu(100): a combined scanning tunneling microscopy and density functional theory study

The adsorption of N(2)O on Cu(100) has been studied by using scanning tunneling microscopy (STM). In the first molecular layer N(2)O forms a densely packed c(3 x 2) structure, in which the molecules occupy two different adsorption sites. The bonding strength of this layer is found to be very weak as revealed by a low desorption temperature and the formation of misalignments and defects. Density functional theory (DFT) finds a stable c(3 x 2) structure in which the molecules are considerably bent due to charge transfer. In model calculations for a 2 x 2 hollow phase we show that in order to reach the chemisorbed, bent configuration, the molecules have to pass an activation barrier. In the experimentally accessible range, this is apparently not possible and the molecules remain in a stable physisorbed state.     

Cu2S-EuS phase diagram

In the Cu₂S-EuS system, a eutectic is formed between Cu₂S- and EuS-based solid solutions (ss) at (1069 ± 2) K, 24.5 mol % EuS. EuS dissolves 7.0 (at 1770 K), 5.0 (1170 K), and 3.0 (770 K) mol % Cu₂S. A ??-Cu₂S-based ss is of the open type, has an extent (mol %) of 15.5 (at 1069 K), 7.5 (970 K), 4.5 (770 K), 2.5 (520 K), and 1.5 (379 K) EuS, and melts incongruently at 1186 K, 7.0 mol % EuS. ??-Cu₂S at 379 K dissolves 6.5 mol % EuS; ??-Cu₂S at (1186 ± 3) K dissolves 3.5 mol % EuS.     

Theoretical Comparison of the Linear and Bent Structures for the Weakly Bound CO2—HF Complex

Density‐functional theory method (DFT) B3LYP/6–311++G(3df,2pd) and Moller‐Plesset perturbation method (MP2) MP2/6–311++G(3df,2pd) of Gaussian 03 were selected for the theoretical study of weakly bound CO₂—HF complex. In addition to the well‐known linear structure, the various bent structure complexes were also found in this work. The self‐consistent energy differences were only around 0.02 kJ/mol between the bent structure and linear structure by comparison. From the results of H‐bonding distance, dHF elongation and red shift of VHF vibration frequency, all the evidence shows that the H‐bonding effect in the bent structure is stronger than the linear structure. However, if one compares the Gibbs energy of the complex formation by temperature variation, it is very easily found that the linear form is favored under the thermal conditions of most temperatures whenever T ≥ 40 K. Such a fact is consistent with the former spectroscopic observed result of Klemperer et al.