An ab initio study on substituent and cooperative effects in bifurcated fluorine bonds

Bifurcated fluorine bond (BFB) interactions are studied in model binary complexes pairing N-formyl formamide derivatives and FX molecules (X = F, CN, NC, CF₃ and CCH) by means of ab initio calculations. The calculated F···O binding distances in these complexes are in the range of 2.813–3.048 Å. The corresponding interaction energies lie in a narrow range, from?2.25 to ?16.49 kJ/mol. The nature of BFBs is analysed by a vast number of methods including molecular electrostatic potential, quantum theory of atoms in molecules, non-covalent interaction index and natural bond orbital methods. According to the energy decomposition analysis, the electrostatic and dispersion effects have a dominant role in the formation of these complexes. The formation of a hydrogen- and lithium-bonding interaction tends to increase the strength of BFBs in the ternary XF:NFF-H:NH₃ and XF:NFF-Li:NH₃ complexes, respectively.     

Tuning of pnicogen and chalcogen bonds by an aerogen-bonding interaction: a comparative ab initio study

Using high-level ab initio calculations, the cooperativity effects between an aerogen-bonding and a pnicogen- or chalcogen-bonding interactions are studied in ternary Y···PH₂CN···ZO₃ and Y···SHCN···ZO₃ complexes (Y?=?NH₃, N₂ and Z?=?Ar, Kr, Xe). A detailed analysis of the structures, interaction energies and bonding properties is performed on these systems. For each set of the complexes, a favourable cooperativity is observed between Z···N and P/S···N interactions, especially in complexes involving NH₃ and XeO₃ molecules. It is found that for a given Y or Z, the amount of cooperativity effects in Y···PH₂CN···ZO₃ complexes are important than Y···SHCN···ZO₃ ones. For each ternary complex considered, the effect of a Z···N aerogen bond on a P/S···N bond is more pronounced than that of a P/S···N bond on a Z···N bond. The mechanism of the cooperativity effects in the ternary complexes is studied by electron density difference, quantum theory of atoms in molecules and natural bond orbital analyses. The solvent effects are also studied on the interaction energy and cooperativity of Z···N and P/S···N bonds in the ternary systems.     

The triel bond: a potential force for tuning anion–π interactions

Using ab-initio calculations, the mutual influence between anion–π and B···N or B···C triel bond interactions is investigated in some model complexes. The properties of these complexes are studied by molecular electrostatic potential, noncovalent interaction index, quantum theory of atoms in molecules (QTAIM) and natural bond orbital (NBO) analyses. According to the results, the formation of B···N or B···C triel bond interactions in the multi-component systems makes a significant shortening of anion–π distance. Such remarkable variation in the anion–π distances has not been reported previously. The strengthening of the anion–π bonding in the multi-component systems depend significantly on the nature of the anion, and it becomes larger in the order Br^? > Cl^? > F^?. The parameters derived from the QTAIM and NBO methodologies are used to study the mechanism of the cooperativity between the anion–π and triel bond interactions in the multi-component complexes.     

基于分子表面静电势参数分析溶剂的极性性质

用理论教育处导出的分子表面静电势参数II和σ^2tot对一系列溶剂的五种极性 批E^N T、π^*、Py、SPP和S‘进行了相关分析,与Catalan的理论热力分析结果进行了比较。结果显示：S‘是一个适用性委有好的溶剂极性参数,而质子性溶剂的E ^NT值、芳香化合物和多卤代化合物的π ^*值和SPP值则存在着一定的非极性因素。     

The influence of halogen-bonding cooperativity on the hydrogen and lithium bonds: an ab initio study

ABSTRACT

Ab initio calculations are carried out to study linear NCH···(NCX)_1–5 and NCLi?…?(NCX)_1–5 clusters (X?=?F, Cl, Br). The aim is to study the influence of halogen-bonding cooperativity on the strength and bonding properties of hydrogen or lithium bond. Particular attention is given to parameters such as binding distances, interaction energies and cooperative energies in these systems. According to our results, the halogen-bonding cooperativity between the NCX molecules has an enhancing effect on the strength of hydrogen and lithium bonds, with an increase of 0.33–0.93 and 0.19–0.43?kcal/mol in NCH···(NCX)_n and NCLi···(NCX)_n, respectively. The enhancing effect of halogen bond on the hydrogen and lithium bond is dependent on the nature of halogen atom, and increases as X?=?F?相似文献   

H2O在Al(111)表面吸附的量子化学研究

用量子化学从头算方法，以原子族Ａｌ１０模拟表面，研究了水在Ａｌ（１１１）表面上不同吸附拉的吸附情况，计算得到了稳定的吸附构型和结合能，结果表明：顶位是其最佳吸附位，而且水在表面能以两种取向被吸附，距表面较远时，Ｈ端靠近表面，然后跨过一能垒到达最佳吸附位，此时氧端靠近表面。在吸附过程中，水向表面转移电荷，导致表面功函降低，在氧原子不加极化函数进，水分子的二次轴垂直于表面时能量最低；当考虑中氧的ｄ轨道     

SiF$lt;sub$gt;2$lt;/sub$gt;($lt;sup$gt;1$lt;/sup$gt;A$lt;sub$gt;1$lt;/sub$gt;)自由基的从头算及势能函数

采用从头算的单双取代的二次组态相互作用方法及耦合簇理论对SiF₂自由基的基态进行结构优化, 发现用单双取代的二次组态相互作用方法配有基组6-311G(2df)计算得到的结构参数、谐振频率、离解能及力常数与实验值最接近并优于文献值. 借助多体项展式理论导出SiF₂自由基的势能函数并绘制了等值势能图. SiF₂自由基对称伸缩振动和旋转势能图显示: 在SiF+F →SiF₂反应通道上有鞍点出现, F原子需要越过4.38 eV的能垒才能生成稳定的SiF₂自由基; 只能通过SiF+F→SiF₂两个等价的通道才能生成稳定的SiF₂ 自由基, 并且该反应是有阈能的吸热反应. 关键词： 2')" href="#">SiF₂ 从头算 势能曲线     

The influence of hydrogen- and lithium-bonding on the cooperativity of chalcogen bonds: A comparative ab initio study

ABSTRACT

The aim of this study is to investigate the influence of a hydrogen- or lithium-bonding interaction on the cooperativity of chalcogen bonds in linear NCH···(OCX)_2–5 and NCLi···(OCX)_2-5 clusters (X?=?S, Se). The nature of interactions in the optimised structures is analysed by means of molecular electrostatic potential, quantum theory of atoms in molecules, natural bond orbital and electron density difference methods. According to our results, the formation of a lithium-bonding interaction in NCLi···(OCX)_2-5 clusters induces a large increase in the strength of X···O chalcogen bonds, and hence their cooperativity. This can be mainly rationalised in terms of the electrostatic nature of chalcogen bonds as well as the fundamental orbital interaction between the interacting OCX subunits. The results of this study provide a theoretical evidence for the tuning of chalcogen bonds cooperativity by a hydrogen- or lithium-bonding.     

氧原子和甲基自由基反应机理的理论研究

用分子轨道从头算和密度泛函理论（DFT）中的B3LYP方法以及适中基组6－311＋G（2df,2p)对氧原子与甲基CH3反应进行了系统的研究。计算给出了通道上各斑点物种的构型参数、振动频率和能量。结果表明：CH2OH比CH3O稳定,能量约低26．63kJ/mol,且生成氢和甲醛为其最主要反应通道。     

简正模型势函数法计算C2v三原子分子力场

采用简亚模型势函数方法,在ａｂ ｉｎｉｔｉｏ水平上计算了Ｈ２Ｏ和Ｈ２Ｓ的分子内价值标和简正内坐标的谐性力学数矩阵对角工根据这两个坐丝毫宰的关系导出了谐性力常数矩阵的其它对角和非对角元。由于避免了三格点的ａｂ ｉｎｉｔｉｏｎ计算拟合,因此计算量较少。由此计算出的分子谐振动频率与实验 令人满意的。还在简正内坐标的简单价力场近似下,计算了力常数和谐振频率。     

用CCSD(T)方法计算基态SH和SD的光谱常数(英文)

利用CCSD(T)方法和系列相关一致基cc-pVXZ及aug-cc-pVXZ(X=D,T,Q,5)对SH和SD分子的基态平衡几何,谐振频率和离解能进行了优化计算.利用优选出的CCSD(T)/aug-cc-pV5Z方法对SH和SD的基态进行单点能计算,并将计算结果拟合成了Murrell-Sorbie函数.利用得到的解析势能函数,计算了SH和SD的其余3个光谱常数(ω_ex_e,α_e和B_c),结果表明:除SD的ω_ex_e值外,其余结果均与实验值符合得相当好,但计算得出的ω_ex_e值与推导出的值25.134 cm~(-1)符合得很好.     

First-principle investigation on the thermodynamics of X_2N_2O(X = C,Si, Ge) compounds

The structures under different pressures, elastic properties, electronic structures and lattice vibrations of the X_2N_2O(X = C, Si, Ge) compounds are investigated by using the first-principle method. Based on the phonon density of state,the thermodynamic properties of the present compounds are studied under different pressures and at different temperatures. The structural parameters including the bond lengths and bond angles are in agreement with available experimental measurements and theoretical calculations. We employ the elastic theory to calculate the nine independent elastic constants(C_(ij)) and the derived elastic moduli(B, G, E, v). Results indicate that these X_2N_2O(X = C, Si, Ge) compounds are mechanically stable and show the brittle behaviors. The electronic properties of the present compounds are analyzed by using the band structure and density of states. The phonon dispersion calculations imply that the present compounds are dynamically stable. Based on the quasi-harmonic approximation, the calculations of the specific heat indicate that the temperature in a range of 0 K–1500 K and pressure in a range of 0 GPa–40 GPa have a large effect on the thermal quantities of Ge_2N_2O,compared with on those of the C_2N_2O and Si_2N_2O compounds.     

Accurate second Kerr virial coefficient of rare gases from the state-of-the-art ab initio potentials and (hyper)polarizabilities

The second Kerr virial coefficient of rare gases is studied in this work using the best ab initio potentials and (hyper)polarizabilities in the literature. The second Kerr virial coefficient of helium-4, helium-3, neon, argon, and krypton and its polarizability component of xenon are computed by the semi-classical method together with the Padé approximant over a wide temperature range. In addition, the uncertainty of second Kerr virial coefficient is estimated from the uncertainties of the ab initio interaction-induced properties. The experimental and theoretical data in the literature is compared with our calculated values to examine the quality of this work. It is shown that our computed values in the supplementary materials are as accurate as the literature data at medium and high temperatures and are more reliable at low temperatures.     

PuH3分子的几何构型及基态附近势能特征计算

目前还没有关于PuH₃的分子结构和分子光谱公开解密的资料与数据.基于密度泛函理论的全数值自洽场计算方法——离散变分方法(DVM),数值解相对论Dirac方程,在自由的钚原子和氢原子波函数的数值基及原子能级基础上计算了PuH₃分子的不同几何结构及势能曲线.等边三角棱锥形PuH₃分子基态的数据为:Pu-H键长=2.097726Å,键角θ(H-Pu-H)=119.102Å,H-H距离为3.616817Å,轨道总能量为-19869.834a.u.,费米能级E_f=-16.856eV.分析了反演对称等价的分子态以及非质心坐标对轨道总能量的影响.比较了PuH₂和PuH₃分子参数的全电子计算结果.     

几种Fe（Ⅵ）化合物的物理性质、电化学性能及稳定性研究

为深入认识高铁化合物的物理性质和电化学性能,采用化学法合成了K2FeO4、BaFeO4、SrFeO4和 K2Sr(FeO4)2等几种高铁化合物,比较研究了这几种高铁化合物的形貌、结构、在不同浓度KOH溶液中的溶解度 及其放电性能.研究结果显示,在这几种高铁化合物中,BaFeO4具有较好的电化学性能.但在实验过程中发现,除 K2FeO4外,其余几种高铁化合物均不稳定,在干燥环境中放置时会发生分解.采用量子化学从头算方法从理论上 分析了高铁化合物的稳定性变化规律.研究结果表明,高铁化合物的稳定性与阳离子对FeO42-的极化作用有很 大关系,极化作用越强,高铁化合物就越不稳定.     

Spectroscopic and ab initio characterization of the conformational states of the bis(perfluoro‐ ethanesulfonyl)imide anion (BETI−)

Ab initio calculations were combined with infrared and Raman studies to spectroscopically distinguish the two conformers of the BETI⁻ or bis(perfluoroethanesulfonyl)imide anion, [N(SO₂C₂F₅)₂]⁻, as was previously done for [N(SO₂CF₃)₂]⁻, the TFSI⁻ anion. BETI⁻ is predicted to exist, as does TFSI⁻, in two conformational states of C₂ and C₁ symmetries, the former being more stable by about 6 kJ mol⁻¹. This conformational isomerism produces weak Raman splittings that can be resolved only at low temperatures. Thus, solutions of LiBETI with glymes cooled down to 113 K exhibit a very intense Raman doublet at ∼745–740 cm⁻¹ characteristic of a quenched conformational equilibrium between the C₂ and C₁ conformers. Annealing of the (G3)₂:LiBETI solvate, where G3 is triglyme, leads to an ordered crystalline phase with all the anions in the C₂ conformation, as in the reference salt Me₄NBETI. This conclusion cannot be extended to all the systems in which the BETI⁻ anion interacts weakly with the cation, however, since the diglyme solvate, (G2)₂:LiBETI, contains both C₁ and C₂ anion conformers (in 2:1 ratio) at low temperatures independent of the sample's thermal history. The conformational splittings are larger in infrared, as illustrated by two absorption bands at 601 and 615 cm⁻¹ associated with the C₂ and C₁ anion conformers, respectively. It is possible to follow the relative intensities of these bands in a LiBETI solution with diglyme above room temperature up to 387 K. The C₂ conformer is found to be more stable than C₁ by 4.7 ± 0.7 kJ mol⁻¹. Copyright © 2006 John Wiley & Sons, Ltd.     

叠氮乙烷二聚体分子间相互作用的理论研究

用abinitioHF/ 6 3 11+ +G 计算求得叠氮乙烷二聚体势能面上三种优化构型和电子结构 .经MP2电子相关校正和基组叠加误差 (BSSE)以及零点能 (ZPE)校正 ,求得分子间最大相互作用能为 -10 .45kJ/mol.二子体系间的电荷转移很少 .由自然键轨道 (NBO)分析揭示了相互作用的本质 .基于统计热力学求得温度为 2 0 0 .0 0～80 0 .0 0K从单体形成二聚体的热力学性质变化     

Quantum mechanical studies on the singlet and triplet potential energy surface of the reactions CF3O2 + I,CF3O + OI and CF3 + OIO

The singlet and triplet potential energy surfaces for the reactions CF₃O₂ + I (1), CF₃O + OI (2) and CF₃ + OIO (3) are investigated using ab initio quantum mechanical methods. Four important isomeric energy minima were found, three on the singlet surface, CF₃OOI, CF₃OIO and CF₃IO₂ and one on the triplet surface ³CF₃OIO. CF₂O + FOI are shown to be the most probable products for all reactions, CF₃O +I and CF₃O + O(³P) are possible for reactions (2) and (3) while the reaction pathway leading to CF₃O +OI is also possible for reaction (3).     

Ab initio calculations on the α^3∑u^＋ state properties of dimer ^7Li2

The comparison between single-point energy scanning （SPES） and geometry optimization （OPT） in determining the equilibrium geometry of the α^3∑u^＋ state for ^7Li2 is made at numerous basis sets such as 6-311＋＋G（2df）, cc-PVTZ, 6-311＋＋G（2df, p）, 6-311G（3df,3pd）, 6-311＋＋G（2df,2pd）, D95（3df,3pd）, 6-311＋＋G, DGDZVP, 6-311＋＋G（3df,2pd）, 6-311G（2df,2pd）, D95V＋＋, CEP-121G, 6-311＋＋G（d,p）, 6-311＋＋G（2df, pd） and 6-311＋＋G（3df,3pd） in full active space using a symmetry-adapted-cluster/ symmetry-adapted-cluster configuration-interaction （SAC/SAC=CI） method presented in Gaussian03 program package. The difference of the equilibrium geometries obtained by SPES and by OPT is reported. Analyses show that the results obtained by SPES are more reasonable than those obtained by OPT. We have calculated the complete potential energy curves at those sets over a wide internuclear distance range from about 3.0α0 to 37.0α0, and the conclusion is that the basis set cc-PVTZ is the most suitable one. With the potential obtained at ccopVTZ, the spectroscopic data （Te, De, D0, ωe,ωeХe, αe and Be） are computed and they are 1.006 eV, 338.71 cm^-1, 307.12 cm^-1, 64.88 cm^-1, 3.41 cm^-1, 0.0187 cm^-1 and 0.279 cm^-1, respectively, which are in good agreement with recent measurements. The total 11 vibrational states are found at J=0. Their corresponding vibrational levels and classical turning points are computed and compared with available RKR data, and good agreement is found. One inertial rotation constant （By） and six centrifugal distortion constants （Dr Hv, Lv, My, Nv, and Ov） are calculated. The scattering length is calculated to be -27.138α0, which is in good accord with the experimental data.     

应变对单层二硫化钼能带影响的第一性原理研究

采用密度泛函理论框架下的第一性原理平面波赝势方法,研究了双轴拉应变下单层二硫化钼晶体的电子结构性质．本文的计算结果表明对单层二硫化钼晶体施加一个很小的应变（0．5％）时,其能带结构由直接带隙转变为间接带隙．随着应变的增加,能带仍然保持间接带隙的特征,且禁带宽度呈现线性下降的趋势．通过对单层二硫化钼晶体态密度和投影电荷密度的进一步分析,揭示了单层二硫化钼晶体能带变化的原因．