镱硫属化合物的密度泛函理论研究

用密度泛函理论(DFT)研究镱硫属化合物的电子结构和性质,通过与实验比较考察了现有的几种近似密度泛函公式对镧系元素化合物的适用程度和相对论效应的影响.结果表明,用DFT计算的YbO键长对实验值的偏差约为0.002nm;但得到的键能即使在考虑梯度校正和相对论效应之后,仍比实验值高,在定域密度近似基础上引入交换梯度校正使键能计算值减小,其中PW86x使键能计算值减小稍多些,结果更接近实验值;相关梯度校正使键能计算值升高.相对论效应使键长缩短0.004～0.006nm,键能减小约0.5eV.计算结果的分析表明,Yb的5d轨道和配体的np轨道间形成σ键和π键.在所研究的分子体系中,配体原子从O到Te、Yb原子的5d轨道布后数依次减少,同键能减弱的顺序一致.相对论效应使键能减小的主要原因是在成键过程中发生了Yb的6s电子向5d轨道的转移,而相对论效应使该过程能量增加.偶极矩和电荷分布的计算表明,Yb-L键以共价性为主,相对论效应使共价性成份增加.     

PdC_2H_2和PtC_2H_2的键结构研究

关于过渡金属Pd,Pt对C_2H_2的吸附和氢化实验研究前人已作了不少工作,但有关Pd,Pt与C_2H_2之间成键问题的理论研究还尚不多见。为了了解Pd,Pt d轨道对炔键的活化行为和成键特性,本文以MC_2H_2(M=Pd,Pt)为模型,用赝势计算方法,对Pd,Pt与C_2H_2键的相互作用进行了研究。一、计算方法由于重原子的内层轨道对形成分子贡献很小,内层电子的相对论效应极为严重。本文采用Ps—HONDO程序,选取Hay的有效核芯势和价轨道Gaussian基组,对重原子Pd和Pt进行了价电子从头计算,对C和H进行了全电子从头算.部分地消除重原子内层电子相对论效应所引起的误差。     

基于三脚架配体构筑的锕系-配体多重键的研究进展

非水溶液体系的锕系元素化学是一个极具挑战性的前沿研究领域, 近年来在分子磁性、多重键以及小分子活化等方面获得了迅速发展. 化学键是化学科学中最重要的基本概念之一, 而金属-配体多重键是该领域重要的研究内容. 多重键的形成与锕系元素的电子结构密切相关, 相对论效应使得锕系元素的s轨道和p轨道收缩, 轨道能量降低, 收缩的s和p轨道增加了对核电荷的屏蔽效应, 从而使d和f轨道具有一定的延展性和不稳定性. 这种不稳定性降低了5f电子的结合能, 电子更容易离去, 可使锕系元素具有丰富的氧化态. 由于较高的主量子数和相对论效应, 锕系元素的5f轨道具有更大的径向延展, 在锕系元素中5f轨道的电子行为影响较大. 目前, 锕系金属-配体多重键因其独特的成键方式和电子结构特征而受到科学家的广泛关注, 在合成和分离方面存在极大的挑战, 研究锕系-配体多重键将有助于我们了解它们的电子结构和反应性. 基于口袋型拓扑结构的三脚架配体被广泛地应用于锕系-配体多重键的研究, 这为探索锕系元素的5f电子结构和锕系多重键丰富的化学行为提供了重要支撑. 本综述总结了近年来基于三脚架配体构筑的锕系-配体多重键的研究进展, 并对未来进行了展望.     

稀土夹心化合物的SCF-Xα-SW研究 Ⅲ.(Cp~2YbCl)~2和(Cp~2ErH)~2

用SCF-Xα-SW 方法非相对论和相对论方案计算了稀土桥键夹心化合物(Cp~2YbCl)~2和(Cp~2ErH)~2能级,轨道等值图形,布居数等的研究表明,(Cp~2YbCl)~2和(Cp~2ErH)~2的共价键比Cp~2Yb和Cp~2YbC~2H~2强而与Cp~3Sm和LnF~3相近. 证实了三价稀土化合物共价键比二价化合物强, 桥键氢原子较小的原子半径和价轨道单位相性质,使氢桥化合物(Cp~2ErH)~2形成比氯桥化合物(Cp~2YbCl)~2更强的共价键,非相对论和相对论计算能级结构,价轨道成分,成键图象等方面的差异, 表明了研究重稀土化合物考虑相对论效应的必要性     

金属四重键化合物M2X4（PMe3）4（M=Cr，Mo，W;X=F，CI，Br，I）结构和电子光谱的密度泛函理论研究

采用密度泛函理论方法，在TZ2P-STO基组水平下，对金属四重键化合物M2Cl4（PMe3）4（M=Cr，Mo，W）和Mo2X4（PMe3）4（X=F，Cl，Br，I）的几何结构进行优化，分析了电子结构，并运用TDDFT方法对其低占据激发态进行了计算．考虑相对论效应的ZORA方法能够较好地重现M2X4（PMe3）4的几何结构．M2X4（PMe3）4的电子结构分析表明其d电子的组态为σ^2π^4δ^2，前线轨道能级顺序为πlig〈πd／σd〈δd〈δd^＊．金属原子和卤素配体的改变虽然使轨道能量发生变化，但没有影响轨道的排布顺序．TDDFT方法对M2Xa（PMe3）4δd→δd^＊和π→δd^＊跃迁能量的计算较为准确，对πlig→δd^＊（LMCT）跃迁能量的计算误差较大．金属原子、卤素配体以及相对论效应对激发能的影响可以根据分子轨道能级的变化给予解释．     

金属四重键化合物M2X4(PMe3)4(M=Cr,Mo,W;X=F,Cl,Br,I)结构和电子光谱的密度泛函理论研究

采用密度泛函理论方法,在TZ2P-STO基组水平下,对金属四重键化合物M2Cl4(PMe3)4(M=Cr,Mo,W)和Mo2X4(PMe3)4(X=F,Cl,Br,I)的几何结构进行优化,分析了电子结构,并运用TDDFT方法对其低占据激发态进行了计算.考虑相对论效应的ZORA方法能够较好地重现M2X4(PMe3)4的几何结构.M2X4(PMe3)4的电子结构分析表明其d电子的组态为σ2π4δ2,前线轨道能级顺序为πlig<πd/σd<δd<δd*.金属原子和卤素配体的改变虽然使轨道能量发生变化,但没有影响轨道的排布顺序.TDDFT方法对M2X4(PMe3)4δd→δd*和πd→δd*跃迁能量的计算较为准确,对πlig→δd*(LMCT)跃迁能量的计算误差较大.金属原子、卤素配体以及相对论效应对激发能的影响可以根据分子轨道能级的变化给予解释.     

抗肿瘤多酸药物[Mo7O24]6-的电子结构研究

运用第一原理密度泛涵理论中的离散变分方法（ＤＦＴ－ＤＶＭ）对具有抗肿瘤活性的多酸药物三合水七钼酸异丙基胺的阴离子「Ｍｏ７Ｏ２４」＾６－进行了电子结构，获得了键级、不等价原子的电子占据数、原子净电荷，分子轨道能级以及「Ｍｏ７Ｏ２４」＾６－的ＨＯＭＯ和ＬＵＭＯ组成等数据，并对该药物的活性和作用机理从电子结构的角度进行了讨论。     

Au12M (M=Na,Mg, Al,Si, P,S, Cl)团簇的结构、稳定性和电子性质

采用基于密度泛函理论的第一性原理方法系统地研究了Au12M(M=Na,Mg,Al,Si,P,S,Cl)团簇的结构、稳定性和电子性质.对团簇的平均结合能、镶嵌能、垂直离化势、最高占据分子轨道(HOMO)和最低未占据分子轨道(LUMO)的能级差、电荷布居分析、自然键轨道(NBO)进行了计算和讨论.对于Au12M(M=Na,Mg,Al)团簇,它们形成了内含M原子的最稳定的笼状结构.然而对于Au12M(M=Si,P,S,Cl)团簇,它们却形成了以M元素为顶点的稳定锥形结构.在这些团簇中发现Au12S团簇相对是最稳定的,这是由于Au12S团簇形成了稳定的满壳层的电子结构.自然电荷布居分析表明:对于所有的Au12M(M=Na,Mg,Al,Si,P,S,Cl)团簇电荷总是从Au原子转向M原子.自然键轨道和HOMO分析表明Au12M团簇中发生了Au原子的s-d轨道和M原子的p轨道间的杂化现象.     

含Hg化合物的相对论赝势从头计算研究——HgX2(X=Cl,Br,I)的电子结构

本文应用相对论赝势从头计算方法, 在不同基组水平上, 系统地研究了卤化汞(HgX_2, X=Cl,Br,I)系列的电子结构。表明除Hg的6s主要参与成键外, 5dz~2也起了重要的作用。并且随卤素原子序的增加, π成键作用也增强。同时还应用单电子自旋-轨道耦合方法, 研究了旋-轨耦合效应的影响, 指定了该系列化合物的光电子能谱。     

水溶液中碳酸铀酰化合物的电子结构

应用相对论密度泛函理论系统研究了水溶液中非水合化和水合化碳酸铀酰化合物Cn/m(其中n和m分别为结构中碳酸配体和水配体的个数)的结构.溶剂效应采用类导体屏蔽模型(COSMO),并采用零级规整近似(ZORA)方法考虑标量相对论效应和旋-轨耦合相对论效应.电子跃迁采用包含旋-轨耦合相对论效应的含时密度泛函理论并在相关交换势中采用轨道势能统计平均(SAOP)做近似计算.结果表明碳酸配体对配合物结构和电子跃迁有很大的影响.C3/0配合物的稳定性可归于5f轨道参与了高占据轨道的成键作用.增加碳酸盐配体导致最大波长的蓝移,并在近可见光区域出现高强度的吸收.     

Why the hydration energy of Au+ is larger for the second water molecule than the first one: skewed orbitals overlap

Using molecular-orbital analysis, we have elucidated the quantum-chemical origin of the intriguing phenomena in sequential hydration energies of the gold cation, which is known to be the most conspicuous among all transition metals. The hydration energy of Au+ with the second water molecule is found to be much larger than that with the first water molecule. Owing to the large relativistic effect of gold (i.e., significant lowering of the 6s orbital energy and significant raising of the 5d orbital energy), the highest occupied molecular orbital of the hydrated gold cation has a large portion of the 6s orbital. As the electron density of the 6s orbital populates in a large outer spherical shell far off the gold nucleus, the p orbitals (or sp hybridized lone-pair orbitals) of the water molecules are able to overlap with the outer part of the 6s orbital in the dihydrated gold cation, resulting in the unusual skewed overlap of p-6s-p orbitals (not the atom-to-atom bond overlap). No previous molecular-orbital analysis has reported this peculiar skewed orbitals overlap. Since this skewed orbitals overlap is saturated with two water molecules, this property is responsible for the low coordination number of the gold ion.     

Ab Initio Theoretical Investigation on the Geometrical and Electronic Structures of AlAun-/0 (n = 2-4) Clusters

A systematic density functional theory and wave function theory investigation on the geometrical and electronic properties of AlAu n 0/-(n=2-4) clusters has been performed in this work. AlAu n-anions prove to possess ground states of the V-shaped C2v AlAu2 - , umbrella-shaped C3v AlAu3- , and perfect tetrahedral T d AlAu4- , while their neutrals favor the V-shaped C2v AlAu2 , perfect planar triangular D3h AlAu3 , and severely distorted C s AlAu4 , respectively. Aluminum aurides appear to be analogous to the corresponding aluminum hydrides, expect C s AlAu4 . Molecular orbitals (MOs) analyses also support this conclusion. Detailed orbital analyses indicate that Au 6s makes 94-96% and Au 5d makes 6-4% contribution to the Au-based orbitals in Al-Au bonds, which is smaller than the BAu n0/- series, partially reflecting the relativistic effect of gold. The one-electron detachment energies of the anions and characteristic stretching vibrational frequencies of Al-Au bonds between 100-400 cm -1 have been calculated to facilitate future experimental characterization of these clusters.     

Revisiting the geometry of nd10 (n+1)s0 [M(H2O)]p+ complexes using four-component relativistic DFT calculations and scalar relativistic correlated CSOV energy decompositions (M(p+) = Cu+, Zn2+, Ag+, Cd2+, Au+, Hg2+)

Hartree-Fock and DFT (B3LYP) nonrelativistic (scalar relativistic pseudopotentials for the metallic cation) and relativistic (molecular four-component approach coupled to an all-electron basis set) calculations are performed on a series of six nd10 (n+1)s0 [M(H2O)]p+ complexes to investigate their geometry, either planar C2v or nonplanar C(s). These complexes are, formally, entities originating from the complexation of a water molecule to a metallic cation: in the present study, no internal reorganization has been found, which ensures that the complexes can be regarded as a water molecule interacting with a metallic cation. For [Au(H2O)]+ and [Hg(H2O)]2+, it is observed that both electronic correlation and relativistic effects are required to recover the C(s) structures predicted by the four-component relativistic all-electron DFT calculations. However, including the zero-point energy corrections makes these shallow C(s) minima vanish and the systems become floppy. In all other systems, namely [Cu(H2O)]+, [Zn(H2O)]2+, [Ag(H2O)]+, and [Cd(H2O)]2+, all calculations predict a C2v geometry arising from especially flat potential energy surfaces related to the out-of-plane wagging vibration mode. In all cases, our computations point to the quasi-perfect transferability of the atomic pseudopotentials considered toward the molecular species investigated. A rationalization of the shape of the wagging potential energy surfaces (i.e., single well vs. double well) is proposed based on the Constrained Space Orbital Variation decompositions of the complexation energies. Any way of stabilizing the lowest unoccupied orbital of the metallic cation is expected to favor charge-transfer (from the highest occupied orbital(s) of the water ligand), covalence, and, consequently, C(s) structures. The CSOV complexation energy decompositions unambiguously reveal that such stabilizations are achieved by means of relativistic effects for [Au(H2O)]+, and, to a lesser extent, for [Hg(H2O)]2+. Such analyses allow to numerically quantify the rule of thumb known for Au+ which, once again, appears as a better archetype of a relativistic cation than Hg2+. This observation is reinforced due to the especially high contribution of the nonadditive correlation/relativity terms to the total complexation energy of [Au(H2O)]+.     

稀土夹心化合物的SCF-Xａ-SW研究 2:Cp~2Yb C~2H~2和Cp~2Yb(OC)~2

用SCF-Xａ-SW方法非相对论和相对论方案计算了Cp~aYb C~2H~2和Cp~2Yb(OC)~2.非相对论主HOMO是Cp的π轨道,相对论间接效应的作用,使得Yb的4f轨道能级上升为HOMO,相对论结果与Yb二价化合物不稳定、易氧化的实验结果一致,也表明了研究重稀土化合物考虑相对论效应的必要性.计算共价键强度与Cp~2Yb相近,比YbF~3和Cp~3SM弱,再次表明二价稀土化合共价键比三价化合物弱.同时也证实了σ型配体(CO)与稀土元素的配 位作用比π型配体(C~2H~2)强的结论.     

Relativistic effects on the Fukui function

The extent of relativistic effects on the Fukui function, which describes local reactivity trends within conceptual density functional theory (DFT), and frontier orbital densities has been analysed on the basis of three benchmark molecules containing the heavy elements: Au, Pb, and Bi. Various approximate relativistic approaches have been tested and compared with the four-component fully relativistic reference. Scalar relativistic effects, as described by the scalar zeroth-order regular approximation methodology and effective core potential calculations, already provide a large part of the relativistic corrections. Inclusion of spin–orbit coupling effects improves the results, especially for the heavy p-block compounds. We thus expect that future conceptual DFT-based reactivity studies on heavy-element molecules can rely on one of the approximate relativistic methodologies.     

Relativistic model core potential study of the Au+ Xe system

A computational study of the Au(+)Xe ionic system has been performed using newly developed coupled-cluster methods and relativistic model core potentials, with extra basis functions optimized to afford superior polarizabilities. Potential energy curves for the dissociation of Au(+)Xe were studied at different levels of theory, and molecular properties (bond length and harmonic vibrational frequency) were calculated. Wave functions were analyzed using the natural bond orbital method. The nature of bonding in this system is discussed.     

Importance of backdonation in [M-(CO)]p+ complexes isoelectronic to [Au-(CO)]+

In this contribution, we study several monocarbonyl-metal complexes in order to unravel the contribution of relativistic effects to the metal-ligand bond length and complexation energy. Using scalar density functional theory (DFT) constrained space orbital variation (CSOV) energy decomposition analysis supplemented by all-electron four-component DFT computations, we describe the dependency of relativistic effects on the orbitals involved in the complexation for the Au(+) isoelectronic series, namely, the fully occupied 5d orbitals and the empty 6s orbitals. We retrieve the well-known sensitivity of gold toward relativity. For platinum and gold, the four-component results illustrate the simultaneous relativistic expansion of the 5d orbitals and the contraction of the 6s orbitals. The consequences of such modifications are evidenced by CSOV computations, which show the importance of both donation and backdonation within such complexes. This peculiar synergy fades away with mercury and thallium for which coordination becomes driven by the accepting 6s orbitals only, which makes the corresponding complexes less sensitive toward the relativistic effects.     

稀土夹心化合物的SCF-X~α-SW研究 I: Cp~2Sm, Cp~2Yb 和Cp~3Sm

对Cp~2Sm、C~p~2Y~b和Cp~3Sm 进行了非相对论和相对论SCF-X~α-SW计算, 用轨道相互作用、分子轨道图形、布居数分析等方法讨论了化学键图象。在Cp~2Ln(Ln=稀土元素)中以Cp为主要成分的轨道能级两种方案结果变化不大。而相对论间接效应的存在, 使Ln4f能级明显升高, 与Cp~2Ln易被氧化的实验结果一致。二价的Cp~2Ln成键轨道中Ln成分是d>f>p>s, 与三价的Cp~3Sm、LnF~3比较, Ln的s、p、d成分变化不大, 而Lnf成分明显减少, 使Cp~2Ln共价性明显地低于Cp~3Sm和LF~3。     

Dependence of relativistic effects on electronic configuration in the neutral atoms of d- and f-block elements

Although most neutral d- and f-block atoms have nd(g-2)(n + 1)s(2) and (n - 1)f(g-2)(n + 1)s(2) ground configurations, respectively, where g is the group number (i.e., number of valence electrons), one-third of these 63 atoms prefer a higher d-population, namely via (n + 1)s-->nd "outer" to "inner" electron shift (particularly atoms from the second d-row), or via (n - 1)f-->nd "inner" to "outer" electron shift (particularly atoms from the second f-row). Although the response to the modified self-consistent field is orbital destabilization and expansion for (n + 1)s-->nd, and stabilization and contraction for (n - 1)f-->nd, the relativistic modification of the valence orbital responses is stabilization in both cases. This is explained by double perturbation theory. Accordingly, electron configuration and relativity trigger the orbital energies, the orbital populations and the chemical shell effects in different ways. The particularly pronounced relativistic effects in groups 10 and 11, the so-called gold maximum, occur because of particularly efficient cooperative nonrelativistic shell effects and relativistic stabilization effects (inverse indirect effect) at the end of the d-block.     

Structures of MAu16 (-) (M=Ag, Li, Na, and K): how far is the endohedral doping?

The structural and electronic properties of MAu16 (-) (M=Ag, Li, Na, and K) have been studied by the scalar relativistic all-electron density-functional calculations, in which particular attention is paid to the stability of the endohedral Au16 (-) cage doped by different dopant atoms. It is found that only the smaller atoms, such as Cu, Li, and Na, can be stably encapsulated in the Au16 (-) cage, while the addition of the larger Ag or K atom prefers to locate in the surface or outside of the cage, which is inconsistent with the previous hypothesis that the Au16 (-) cage could act as a container to hold an arbitrary heterometal atom. The stable endohedral Li@Au16 (-) and Na@Au16 (-) have a large energy gap between the highest occupied molecular orbital and the lowest unoccupied molecular orbital gap, indicating that they are chemically stable and may be used as potential building blocks for designing cluster-assembled materials.