结构参数X的计算方法及与分子总键能和生成焓的关系

本文借助于电负性I和有效主量子数n_i^*定义了有效价电子数Z_i′。由Z_i′、 n^*_i及成键电子数mi定义的原子结构参数δ_i和分子结构参数X被计算。发现A_mB_n型分子的X相似文献   

有效主量子数拓扑指数与分子总键能和晶格能的关系

作者定义ＡｊＢｋ分子的有效主量子数拓扑指数（Ｐ）为：Ｐ＝∑（ｎＡ·ｎＢ）－０．５。它与化合物的总键能（ΔＥ）、晶格能（Ｕ）呈现高度相关性,其直线回归方程为：ΔＥ＝－２８．４５１８＋１１１７．８９８Ｐ,Ｒ＝０．９３５４Ｕ＝１９６．６７０３＋１６６５．６２６６Ｐ,Ｒ＝０．９８８２用它预测ΔＥ、Ｕ,估算值与实验值基本吻合     

结构参数F1对气态ABn型分子标准生成焓的定量关系研究

本文用矩阵的方法定义了结构参数Ｆ_１,Ｆ_１由三个矩阵相乘得到一个无量纲的数,它考虑了分子中原子之间的联结关系,顶点原子的特点和相邻原子的成键情况。用 Ｆ_１对 １１６个气态 ＡＢ_ｎ型分子的标准生成焓进行相关性研究,相关系数Ｒ为０．９５６０。     

碱金属双原子分子的键电子与键能的关系

本文通过量子化学从头计算了，对碱金属双原子分子的成键情况进行了研究，并对它们的异常现象提出了一种较为合理的解释。     

有机化学中几个键参数的讨论

有机化学中几个键参数的讨论周文富，赖文忠（福建三明师专化学系３６５００４）有机化学中共价键的一些重要属性，如键能、键长等。这些属性是判断有机分子结构和性质的重要参数；近年已引起不少学者的相继讨论￣［１－４］。有些教科书和文献在理论上提法的准确性不够。...     

键能的分子轨道理论研究2: 键能与Mulliken布居对键强度的 判断的比较

用键能E~A~B和Mulliken布居对化学键强度的判别进行了分析比较。结果表明,键能判据比Mulliken布居判据所得结论更符合实际情况。作为衡量原子间化学键强度的尺度,不仅应考虑原子轨道间的布居因素,还应考虑分子轨道(或原子轨道)的能量因素。     

键能的分子轨道理论研究2: 键能与Mulliken布居对键强度的 判断的比较

用键能E~A~B和Mulliken布居对化学键强度的判别进行了分析比较。结果表明,键能判据比Mulliken布居判据所得结论更符合实际情况。作为衡量原子间化学键强度的尺度,不仅应考虑原子轨道间的布居因素,还应考虑分子轨道(或原子轨道)的能量因素。     

键长与价层轨道平均能的关系

关于键长的计算方法颇多。本文试从键长与原子价层轨道平均能的关系建立一个简单且更接近实验值的计算公式。我们知道,对于每个成键原子来说,一方面作为带电体使对方电子云发生变形;另一方面在对方的作用下,本身发生变形。如果成键原子吸引键合电子的能力相等,各自的电荷分布将很少变化,键长就等于成键     

结构参数x′与A_mB_n型无机物晶格焓和标准生成焓的关系研究

Ｒａｎｄｉｃ－Ｋｉｅｒ提出的价连接性指数［１,２］在有机分子的构效关系研究中得到了广泛应用。但因其顶点价连接性值δｖ不反映原子的氧化状态,以及价电子数不能准确描述过渡元素的成键情况,故不能应用于无机体系,本文定义的价连接性值δｉ′包含了成键电子数和有...     

Pure through‐bond state in organic molecules for analysis of the relationship between intramolecular interactions and total energy

Ab initio configuration interaction through‐space/bond interaction analysis was proposed for the examination of specific intramolecular interactions including the effect of electron correlations. To test the effectiveness of our method, we applied it to rotational barrier in ethane. The results of our test suggest that the insensitivity of the ethane barrier to geometric relaxations is intimately connected with the cancellation of interactions through orbital overlaps and other factors. The orbital overlaps include exchange repulsion and hyperconjugation; other factors include classic Coulomb interaction and changes in bond orbital energy. The rotational state without the barrier (pure through‐bond state) can be achieved by deleting not only the “vicinal” interactions between the C? H bonds that belong to different methyl groups but also the “geminal” interactions within the methyl groups. Our mixing analysis of molecular orbitals supports the superiority of the staggered conformer by hyperconjugation. Moreover, it was demonstrated that our treatment could be applied to excited states as well as to the ground state, including electron correlation effects. © 2003 Wiley Periodicals, Inc. Int J Quantum Chem, 2003     

Relationship between the energy of donor–acceptor bond and the reorganization energy in molecular complexes

Donor–acceptor complexes of silicon halides with ammonia, pyridine, and 2,2′bipyridine SiX₄ · nD (X = F, Cl, Br) have been studied at the B3LYP/pVDZ level of theory. Energies of the donor–acceptor bond have been estimated taking into account the reorganization energy of the donor and acceptor fragments and basis set superposition error correction. Despite of the very low (or even negative) dissociation energy of SiX₄ · nD into free fragments, the Si–N bonding in all complexes is rather strong (75–220 kJ mol^?1). It is the reorganization energy of the acceptor SiX₄ (75–280 kJ mol^?1) that governs the dissociation energy of the complex. Thus, in contrast to the complexes of group 13 halides, the reorganization effects are crucial for the complexes of group 14 halides, and their neglecting leads to erroneous conclusions about the strength of the donor–acceptor bond in these systems. © 2002 Wiley Periodicals, Inc. Int J Quantum Chem, 2002     

A new approach to the relationship between bond energy and electronegativity

The familiar equation whereby Pauling related heteronuclear bond energies D_A–B to the electronegativity difference Δχ (=∣χ_A − χ_B∣) and the homonuclear bond energies D_A–A and D_B–B has been the subject of critical scrutiny for at least half a century. A modification to this equation that combines the concepts of electronegativity and hardness/softness can be rewritten in terms of two quantities x and y, both having absolute significance. Both homo- and heteronuclear bond energies can be rationalised from these new equations. The quantities x are linearly related to Pauling electronegativities, while y appears to be a measure of an atom’s intrinsic bonding potential, related to size and availability of valence orbitals.     

键连接性指数的建构及其在有机体系中的应用研究

以化学键为基础建构了键连接性指数及分子键连接性指数，该指数同时考虑顶 点原子的化学特征及键的性质．对于任意化学键，键连接性指数Si＝1+△I/R·[（ Z1-h1)m2/n1+(Z2-h2)m1/n2]，分子键连接性指数S为∑i=1^m√Si或∑i=1^m1/√ Si，其中，Z1，Z2为化学键键连原子的价电子数；n1，n2成键原子的价层最高主量 子数；m1，m2为成键原子的氧化数；h1，h2为与成键原子相连的氢原子个数；△I 为成键原子的电负性差(△I≥0)；R为化学键的相对键长．与以顶点为基础的价连 接性指数不同，该指数不仅能方便而有效地应用于饱和碳氢体系亦能有效地应用于 含多重键的不饱和体系及含杂原子的有机体系．研究了饱和碳氢体系标准生成焓， 不饱和碳氢体系和酮、醚、酯体系在水中的溶解度和辛醇/水分配系数，卤代甲烷 体系的标准生成焓，卤代苯体系辛醇/水分配系数，均取得比较满意的结果。     

烷烃中碳氢键离解能的估算及其应用

将烷烃中的C－H键看成氢原子H与烷基Ri相连接而成的Ri－H键，以烷基的 HOMO能级和氢原子的轨道能来关联Ri－H键的离解能BDE。研究表明，烷烃分子中 Ri－H键的离能BDE与烷基Ri的极化效应指数PEI（Ri）有良好的线性关系：BDE＝ c+dPEI(Ri)。所得方程具有良好的估算精度。烷基Ri极化效应指数PEI（Ri）在羟 基自由基与烷烃反应速度常数的定量相关中，也得到良好的应用。     

Simple wavefunctions for dipositronium and the relationship between this species and the hydrogen molecule

Dipositronium (two electrons and two positrons) has a closer relationship to the hydrogen molecule than has often been assumed in past treatments. This article shows that appropriately modified mixtures of simple molecular orbital and Heitler–London wavefunctions are a good basis for the ground state of this species. © 2003 Wiley Periodicals, Inc. Int J Quantum Chem, 2004     

键能的分子轨道理论研究 1: 理论公式

从LCAO-MO出发, 给出了一个计算键能的近似方法, 即EAB(i)-∑∑CaiSabCbiεi为第i个占据分子轨道(MO)中的一对电子对A-B键键能的贡献。对所有分子轨道求和即为该键的键能: EAB=∑EAB(i)。按该方法, 不仅可以计算各种不同分子中每两个相键连原子间的键能, 还可以从MO及AO角度分析每一具体键, 如σ, π, δ键的键能以及各AO对键能的贡献。该方法虽有别于求键焓和平衡离解能De, 但计算结果和De的实验值甚相符合。通过对键能的分析研究, 能较好地揭示原子间的相互作用关系及化学键的强弱, 从而可进一步探讨化学反应活性, 反应速率等化学性质。     

He2@C60: Thoughts of the concept of a molecule and of the concept of a bond in quantum chemistry

We present a broad palette of discussions of the concepts of a molecule and a chemical bond that always lay down behind all computational modeling in quantum chemistry and of the endohedral fullerene He₂@C₆₀ in particular. For this purpose, we offer the definition of quantum chemistry as composed of three ingredients. Each of them is illustrated by its particular concept, either that of a molecule or a bond. The third, computational ingredient is tackled to resolve the bonding manifold of He₂@C₆₀ and to demonstrate that van‐der‐Waals binding of He? He is converted within He₂@C₆₀ into a stronger bond due to that C₆₀ acts as an electronic buffer and [He₂] moiety mimics a fractionally charged . Experimental fingerprints of He₂@C₆₀ are computed. © 2015 Wiley Periodicals, Inc.