金红石TiO2纳米团簇与铀酰相互作用的相对论密度泛函理论计算

采用全电子相对论密度泛函理论方法探索金红石型Ti O_2纳米团簇与铀酰的相互作用。考察金红石团簇模型(包括层数和表面积大小)变化对吸附铀形成复合物结构、吸附作用能等性质的影响,确定2层、表面积为1.1 nm×0.6 nm、包括63个原子的纳米团簇(标记为2L-Ti15)能够合理描述金红石纳米粒子性质的同时,还能节约计算资源。对2L-Ti15-[(UO_2)(H_2O)_3]~(2+)复合物计算表明,纳米团簇和铀酰存在共价键作用;优化得到U-O_(surf)键长0.233~0.238 nm,这一距离在已发现铀酰基配合物U-O距离范围内。在气相条件下,纳米团簇对铀酰吸附反应为放热过程(-3.02 e V);考虑溶剂介质环境的影响,反应则需要吸收少许能量(0.16e V)。U-O_(surf)键的能量分解发现,纳米团簇和铀酰的化学键作用为轨道相互作用主导的(占94%),它的静电吸引略大于Pauli排斥。基于电子密度的QTAIM(quantum theory of atoms in molecule)分析揭示,U-O_(surf)作用是介于离子和共价之间的配位键,其强度高于复合物中的U-OH_2键作用,但比U=O键弱。波函数分析表明,来自纳米团簇的O(2p)贡献HOMO轨道,并混有σ(U=O)成键性质,而LUMO轨道则为Ti(3d)修饰的U(5f)性质,复合物HOMO-LUMO带隙为2.40 e V,相对吸附前的纳米团簇半导体粒子的3.35 e V变窄。从吸收光谱角度而言,复合物体系可能在可见光区域具有更强的捕光性能。     

Relativistic and Non‐Relativistic Electronic Molecular‐Structure Calculations for Dimers of 4p‐, 5p‐, and 6p‐Block Elements

We report results of non‐relativistic and two‐component relativistic single‐reference coupled‐cluster with single and double and perturbative triple excitations [CCSD(T)] treatments for the 4p‐block dimers Ga₂ to Br₂, the 5p‐block dimers In₂ to I₂, and their atoms. Extended basis sets up to pentuple zeta are employed and energies extrapolated to the complete basis‐set limit. Relativistic and non‐relativistic results for the dissociation energy D_e are in close agreement with each other and previously published data, provided non‐relativistic or scalar‐relativistic results are corrected for spin–orbit contributions taken from the literature. An exception is Te₂ where theoretical results scatter by 0.085 eV. By virtue of this agreement it is unexpected that comparison with the experimental D₀ or D_e dissociation energies (zero‐point vibrational effects are negligible in this context) reveal errors larger than 0.1 eV for Ga₂, Ge₂, and Sb₂. Only relativistic treatments are presented for the 6p‐block cases Tl₂ to At₂. Sufficient agreement with experimental data is found only for Pb₂ and Bi₂, the deviation of the computed and experimental D₀ values for Po₂ is again larger than 0.1 eV. Deviations of 0.1 eV between the computed and experimental D₀ values are a major reason for concern and call for additional investigations in both fields to clarify the situation.     

Interaction of copernicium with gold: Assessment of applicability of simple density functional theories

Interactions of Cn (element 112) atom with small Au clusters are studied using accurate ab initio scalar relativistic coupled cluster method for correlation treatment and two‐component relativistic density functional theory (RDFT) to take account of spin‐dependent relativistic effects. The results demonstrate the failure of RDFT with simple generalized‐gradient and hybrid functionals in describing Cn–Au bonds in complex systems. © 2013 Wiley Periodicals, Inc.     

The HgF2 Ionic Switch: A Triumph of Electrostatics against Relativistic Odds

A remarkable transition in the chemical bonding in (HgF₂)_n clusters as a function of n is identified and characterized. HgF₂ is a fascinating material. Certain significant consequences of relativistic effects on the structure of the HgF₂ molecule, dimer, and trimer disappear in the extended solid. Relativistic effects in Hg ensure that HgX₂ molecules (X≡F, Cl, Br, and I) are linear, rigid, and form weakly bound dimers and trimers held together by weak electrostatic and van der Waals‐type forces (unlike ZnX₂ and CdX₂ systems in which the intermonomer contacts are strong polar covalent bonds). For HgF₂, the location and nature of an apparent transition from weak interactions in the smallest (HgF₂)_n clusters to ionic bonding in the (fluorite) HgF₂ extended solid has remained a mystery. Computational evidence obtained at the M06‐2X, B97D3, and MP2 levels of theory and reported herein indicate that polar covalent bonding in (HgF₂)_n begins as early as n=5. For n=2 through to n=13, the transition or switch from weak (primarily dipole–dipole‐type) intermonomer interactions to a preference for polar covalent bonding occurs within the range 5<n≤9. Thermodynamic evidence for this transition is provided. Our results demonstrate a significant risk associated with crystal structure prediction from the ground up (i.e., based on bonding patterns in small clusters). The path from monomers through to extended solids may be punctuated at one or several points (as n increases) with transitions in structure and bonding that are not anticipated or betrayed by the bonding in small clusters.     

Benchmark Calculations on the Atomization Enthalpy, Geometry and Vibrational Frequencies of UF6 with Relativistic DFT Methods

Benchmark calculations on the molar atomization enthalpy, geometry, and vibrational frequencies of uranium hexafluoride （UF6） have been performed by using relativistic density functional theory （DFT） with various levels of relativistic effects, different types of basis sets, and exchange-correlation functionals. Scalar relativistic effects are shown to be critical for the structural properties. The spin-orbit coupling effects are important for the calculated energies, but are much less important for other calculated ground-state properties of closed-shell UF6. We conclude through systematic investigations that ZORA- and RECP-based relativistic DPT methods are both appropriate for incorporating relativistic effects. Comparisons of different types of basis sets （Slater, Gaussian, and plane-wave types） and various levels of theoretical approximation of the exchange-correlation functionals were also made.     

相对论效应和重原子簇的化学、光谱性质

介绍了作者运用多组态自洽场／组态相互作用及相对论组态相互作用的相对论从头计算方法研究重原子簇的化学，光谱性质组的结果， 相对论效应对重要子簇化学，光谱性质的重要影响。     

尿素晶体介电性能的量子化学计算

利用量子化学的第一性原理,在自洽场理论水平上对尿素晶体的线性和非线性光学介电性质进行了定量计算,获得了与实验值相符的理论计算结果.提供了一种解决分子晶体量子化学理论计算的新思路.     

Relativistic and non-relativistic local-density functional, benchmark results and investigation on the dimers

Using two spinor minimax method combined with finite element methods accompanied with extrapolation and counterpoise techniques enable us to obtain relativistic highly accurate results for two atomic molecules. Like in our previous work for the (Hartree-) Dirac–Fock–Slater (DFS) functional we investigate in this work the density functional approximations of the relativistic and non-relativistic local-density functional, presenting highly accurate benchmark results of chemical properties on the dimers of the group 11 (Ib) of the periodic table of elements. The comparison with experimental values and literature’s results shows that DFS is better behaved than the other two local functionals.     

Sol-Gel Synthesis and Gas Adsorption Properties of CuCl Modified Mesoporous Alumina

Cuprous chloride (CuCl) modified unsupported -alumina membranes and adsorbent granules were synthesized by sol-gel processing followed by wet-impregnation of CuCl. The CuCl coated -alumina remains mesoporous with a uniform pore size distribution and a large surface area. The mesoporous alumina granules, prepared by a sol-gel oil-drop process, exhibit excellent mechanical strength and attrition resistance. The CuCl modified -alumina preferentially adsorbs ethylene and carbon monoxide, with a saturated adsorption capacity of 0.67 and 0.78 mmol/g, respectively. Both equilibrium capacity and kinetic rate for adsorption of ethylene and carbon monoxide on the CuCl modified -alumina are much larger than those for ethane and carbon dioxide. These results indicate the potential use of the sol-gel derived CuCl modified -alumina for separation of ethylene or carbon monoxide from its gas mixture containing ethane or carbon dioxide.     

单核锌双卟啉配合物构象平衡的理论研究及光谱分析

合成了一系列以不同长度柔韧链相连的p/p型单核锌双卟啉配合物。选用Tripos力场,利用分子动力学模拟退火和分子力学构象搜索相结合的方法对该系列双卟啉进行了能量优化和构象分析。理论计算结果表明:该类双卟啉稳定存在的最低能量构象为叠合式,最高能量构象为伸展式,并存在一系列的中间能量构象;双卟啉分子内π-π作用和能量转移与双卟啉存在的两种主要构象密切相关;分析了分子内π-π作用的本质。运用不同光谱测试手段验证了理论计算结果: 利用可见和相应二阶导数吸收光谱研究了双卟啉主要存在的叠合式和伸展式构象,通过红外光谱观察了对双卟啉构象和卟啉环间π-π作用较为敏感的吸收谱带;利用荧光光谱计算了双卟啉的分子内能量转移效率。     

Spectroscopic and Chemical Properties of Ionic Liquids: Computational Study

A brief account is given of highlights of our computational efforts – often in collaboration with experimental groups – to understand spectroscopic and chemical properties of ionic liquids (ILs). Molecular dynamics, including their inhomogeneous character, responsible for key spectral features observed in dielectric absorption, infra-red (IR) and fluorescence correlation spectroscopy (FCS) measurements are elucidated. Mechanisms of chemical processes involving imidazolium-based ILs are illustrated for CO₂ capture and related reactions, transesterification of cellulose, and Au nanocluster-catalyzed Suzuki cross-coupling reaction with attention paid to differing roles of IL ions. A comparison with experiments is also made.     

载铜活性炭吸附一氧化碳的密度泛函理论计算

应用密度泛函理论和相对论有效核势方法, 用C₁₆H₁₀, C₁₃H₉, C₁₂H₁₂原子簇模型模拟活性炭表面, 计算得到了CO在载铜活性炭上的吸附位、吸附构型和吸附能. 研究表明: 载铜活性炭吸附CO的过程, 本质上是Cu(I)通过σ-π配键与CO络合, 形成Cu—C键的过程. 载铜活性炭对CO的络合吸附能在50～60 kJ/mol之间, 远大于活性炭对CO的物理吸附能(9.15 kJ/mol), 因而络合吸附更稳定, 选择性也更高. Cu(I)选择吸附在活性炭表面的顶位和桥位, 一个Cu(I)至多可以吸附一个到两个CO分子, 但吸附一个CO比吸附两个CO稳定.     

Metalloid Cluster Compounds of Group 14: Bonding Properties and Subsequent Reactions

Abstract

Metalloid cluster compounds of group 14 of the general formulae E_nR_m with n > m (E = Si, Ge, Sn, Pb; R = ligand), where naked as well as ligand bound tetrel atoms are present, represent a novel class of cluster compounds in group 14 chemistry and can be seen as intermediates on the way to the elemental state. Therefore, interesting properties are expected for these compounds, which might complement results from nanotechnology. In this article, first results for germanium are discussed, together with novel build-up reactions on the way to novel materials based on metalloid cluster compounds.

GRAPHICAL ABSTRACT     

六聚吡咯大环与铀/超铀酰基离子相互作用:成键、热力学和光谱性质

采用全电子相对论密度泛函理论探索多种六聚吡咯大环锕酰基配合物(nAn;n=1~3;An=U,Np and Pu)的电子结构本质、成键规律和化学反应特性。结构优化发现大环配体空穴大小与锕酰离子尺寸相当时,配合物锕酰基采用性对规则的六角双锥结构,而当空穴尺寸相对大时,配合物则采取扭曲结构以降低体系能量。当配体相同时,随着铀、镎、钚变化,An=O伸缩振动频率逐渐变小,这与优化的键长和键级变化规律相一致。QTAIM(quantum theory of atoms in molecule)拓扑分析显示An-N为弱共价单键特征,具有较大离子性成分。依据不同铀源,得到与大环配体的反应自由能均小于146 kJ·mol~(-1),与实验合成配合物的反应能计算数值相当。对含铀配合物电子吸收光谱计算显示,低能(近红外和可见光区)的吸收带具有全部或较大的配体→金属电荷转移性质贡献。     

Calculations of the distribution of trace impurities in cylindrical pores

The equilibrium distribution of a trace impurity and the self-diffusion coefficients of molecules of the base component and the trace impurity in narrow cylindrical pores were calculated using the lattice-gas model. Two types of lattice structures with six and eight closest neighbors were considered. The sizes of the base component and impurity molecules were taken to be identical. Lateral interactions were taken into account in the quasi-chemical approximation. The equilibrium distributions of the trace impurity across a pore section in the gas and liquid phases of the base component and at the interface for the case of capillary condensation were considered. The probability of existence of isolated dimeric clusters was estimated and the self-diffusion coefficients of the base component and trace impurity for a single-phase distribution of the base component were calculated. The effects of the energy of interaction of impurities with the pore walls and the concentration of the base component on the diffusion mobility of the impurities were analyzed. The concentration dependences of the partition coefficient for the trace impurity between the pore center and the pore wall and the concentration dependences of the self-diffusion coefficients for the trace impurity molecules become nonmonotonic with an increase in the base component concentration. These effects are due to the displacement of the impurity from the near-surface area to the bulk of a pore following an increase in the pore coverage by the base component and to higher mobility of the impurity in the free bulk of the pore. Further filling of the pore bulk reduces the mobility of all molecules. The energetics of intermolecular interactions also plays a certain role. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 4, pp. 605–615, April, 2000.     

Solvatochromic shifts of Br2 and I2 in water cages of type 512, 51262, 51263, and 51264

Despite the relatively small size of molecular bromine and iodine, the physicochemical behavior in different solvents is not yet fully understood, in particular when excited‐state properties are sought. In this work, we investigate isolated halogen molecules trapped in clathrate hydrate cages. Relativistic supermolecular calculations reveal that the environment shift to the excitation energies of the (nondegenerate) states and lie within a spread of 0.05 eV, respectively, suggesting that environment shifts can be estimated with scalar‐relativistic treatments. As even scalar‐relativistic calculations are problematic for excited‐state calculations for clathrates with growing size and basis sets, we have applied the subsystem‐based scheme frozen‐density embedding, which avoids a supermolecular treatment. This allows for the calculation of excited states for extended clusters with coupled‐cluster methods and basis sets of triple‐zeta quality with additional diffuse functions mandatory for excited‐state properties, as well as a facile treatment at scalar‐relativistic exact two‐component level of theory for the heavy atoms bromine and iodine. This simple approach yields scalar‐relativistic estimates for solvatochromic shifts introduced by the clathrate cages. © 2015 Wiley Periodicals, Inc.     

卤素氮氧化物的结构和光谱性质的理论研究

通过DFT/B3LYP计算,优化了卤素氮氧化物XNO_2及其异构体XONO（X = F,Cl ,Br,I）的平衡几何构型,预测了异构体的相对稳定性及其相互转化的活化能垒 。在B3LYP和QCISD（T）计算水平上,确定了X-NO_2键的解离能。应用与时间有关 的密度泛函理论（TD-B3LYP）计算了XNO_2低激发态的跃迁能,并讨论了这些激发 态与卤素氮氧化物光诱导解离过程的关联。     

Co-Y共掺杂ZnO光电性质的第一性原理计算

采用基于密度泛函理论(DFT)的第一性原理平面波赝势法研究了本征ZnO、Co和Y单掺杂ZnO、Co-Y不同配位共掺杂ZnO的电子结构和光学性质。计算结果表明,在本文的掺杂浓度下,Co和Y单掺杂可以提高ZnO的载流子浓度,从而改善ZnO的导电性,Co-Y共掺时ZnO半导体进入简并状态,呈现金属性。Co掺杂ZnO会在可见光和近紫外区域发生吸收增强现象,而Y掺杂ZnO可以提高体系在紫外区域的吸收,其中由于Co离子和Y离子之间的协同效应,Co-Y共掺ZnO时体系对可见光和近紫外区域的光子能量吸收大幅增加,因此Co-Y共掺杂ZnO可以用于制作光电感应器件。     

Co-Y共掺杂ZnO光电性质的第一性原理计算

采用基于密度泛函理论(DFT)的第一性原理平面波赝势法研究了本征ZnO、Co和Y单掺杂ZnO、Co-Y不同配位共掺杂ZnO的电子结构和光学性质。计算结果表明,在本文的掺杂浓度下,Co和Y单掺杂可以提高ZnO的载流子浓度,从而改善ZnO的导电性,Co-Y共掺时ZnO半导体进入简并状态,呈现金属性。Co掺杂ZnO会在可见光和近紫外区域发生吸收增强现象,而Y掺杂ZnO可以提高体系在紫外区域的吸收,其中由于Co离子和Y离子之间的协同效应,Co-Y共掺ZnO时体系对可见光和近紫外区域的光子能量吸收大幅增加,因此Co-Y共掺杂ZnO可以用于制作光电感应器件。