三原子共价分子的几何构型

一三原子共价分子的几何构型,经实验测定,不外乎是分属线型及V型两种不同类型。对主族元素所构成的分子,一般用以解释     

三原子分子振转激发态的理论研究

三原子分子振转激发态的理论研究谢代前,鄢国森,田安民（四川大学化学系,成都,６１００６４）关键词振转激发态,三原子分子,变分法能级较高的振转激发态通常包含大振幅运动,其波函数分布于很广的势能面区域内,传统的正则模理论已不适合于解决这类问题．近年来,Ｈ...     

确定三原子分子势能面的SCF-CI方法

建议根据振动高激发态的实验能级确定三原子分子势能面的SCF-CI方法.此法中使用键长-键角内坐标系下的SCF-CI方法来精确地计算振动高激发态的能级及其对势能参数的一阶微分,并使用LMF算法来优化势能参数.为验证此方法,优化了水分子的势能面,计算出水分子的振动高激发态能级与70个观测到的振动能级相比较,标准偏差为1.15cm~(-1).     

三原子分子振转激发态成簇现象理论研究

在只考虑弯曲振动与总角动量的耦合,而冻结伸缩振动的模型下,采用Jacobi多项式作为弯曲振动的基函数,用严格的变分法研究了H_2O分子的振转激发态的成簇现象.本文计算了H_2O分子的振转能级和函数,研究了振动激发态下转动高激发态光谱中出现的成簇态.     

三原子分子振转激发态成簇现象理论研究

在只考虑弯曲振动与总角动量的耦合,而冻结伸缩振动的模型下,采用Jacobi多项式作为弯曲振动的基函数,用严格的变分法研究了H~2O分子的振转激发态的成簇现象。本文计算了H~2O分子的振转能级和函数,研究了振动激发态下转动高激发态中出现的成簇态。     

两体扰动势和H2O通道反应的三原子体系解析势

提出了两体扰动势的概念.通过两体扰动势构造多原子相互作用体系解析势的理论方法,获得了非线性三原子H2O相互作用体系的解析势函数.用势能面正确描述了O(1D)+H2→H2O→OH+H通道反应的性质.理论分析和实验结果非常符合.该方法比较容易推广构造多原子相互作用体系解析势.     

氮的三原子化合物的从头算及密度泛函研究

在6-311+G*基组水平上,对氮的三原子化合物N3-、N3、N3+,用MP2及六种密度泛涵方法进行了研究.结果表明,对于已知结构的化合物的计算结果与实验测定值非常吻合,对实验上未知的化合物分子的稳定几何构型及其有关参数进行了新的探讨和补充,同时比较了N3-、N3、N3+间相对稳定性和几何性质,并讨论了几种不同方法对该化合物系列诸性质参数的影响,结合MO理论及成键能的计算结果进行了成键分析.     

两体扰动势和H2O通道反应的三原子体系解析势

提出了两体扰动势的概念.通过两体扰动势构造多原子相互作用体系解析势的理论方法,获得了非线性三原子H2O相互作用体系的解析势函数.用势能面正确描述了O（1D）＋H2→H2O→OH＋H通道反应的性质.理论分析和实验结果非常符合.该方法比较容易推广构造多原子相互作用体系解析势.     

Periodic tables of diatomic and triatomic molecules

The Mendeleev periodic table of atoms is one of the most important principles in natural science. However, there is shortage of analog for molecules. Here we propose two periodic tables, one for diatomic molecules and one for triatomic molecules. The form of the molecular periodic tables is analogous to that of Mendeleev periodic table of atoms. In the table, molecules are classified and arranged by their group number G, which is the number of valence electrons, and the periodic number P, which represents the size of the molecules. The basic molecular properties, including bond length, binding energy, force constant, ionization potential, spin multiplicity, chemical reactivity, and bond angle, change periodically within the tables. The periodicities of diatomic and triatomic molecules are thus revealed. We also demonstrate that the periodicity originates from the shell-like electronic configurations of the molecules. The periodic tables not only contain free molecules, but also the "virtual" molecules present in polyatomic molecules. The periodic tables can be used to classify molecules, to predict unknown molecular properties, to understand the role of virtual molecules in polyatomic molecules, and to initiate new research fields, such as the periodicities of aromatic species, clusters, or nanoparticles. The tables should be of interest not only to scientists in a variety of disciplines, but also to undergraduates studying natural sciences.     

Periodic trends in constants of triatomic molecules

Working from the arrangements of both row and group numbers developed within Mendeleev's periodic table of elements, periodic trends can be shown to exist in many constants of triatomic molecules: an extension of the Periodic Law for atoms to the realm of molecules. Trends are identified for vibrational frequencies, bond lengths, and to a lesser extent interior angles. This work includes empirical sources for such data, supplemented with calculations using diatomic analogs where possible. Otherwise, computation is used for all possible configurations of row two and row three main‐group elements to both corroborate and extend empirical results. Organization of this data into a detailed, highly symmetric, multidimensional coordinate system allows for robust graphical and statistical analysis of all constants and associated trends, which in turn permits rapid identification of suspect data to be rechecked. All collected empirical and computational data, along with several interactive visualizations highlighting these results, is available online. © 2016 Wiley Periodicals, Inc.     

Simple electrostatic models for vibrating unsymmetrical triatomic molecules and triatomic ions

Bond charge, point-dipole models are used to derive simple universal relations,K =0.0435 (K₁₁ K ₂₂)^1/2 –0.0086 (K ₁₁ ⁺ K ₂₂), andK = 0.11 (K ₁₁ K ₂₂)^1/2 –0.0055 (K ₁₁ +K ₂₂), between the bond stretching force constantsK ₁₁ andK ₂₂ and bond bending force constantK for linear and bent unsymmetrical triatomic molecules respectively. The relations are shown to be approximately valid for a number of molecules. An extension of the models to include charged species (ions) in triatomic molecules is also presented and tested, giving good results.Based on part of a thesis submitted by José L. Gázquez in partial fulfillment of the requirements for the degree of Doctor of Philosophy, The Johns Hopkins University, 1976, and aided by research grants to the Johns Hopkins University and University of North Carolina from the National Institutes of Health and the National Science Foundation.     

Potential energy surface for linear triatomic molecules: An algebraic method

Recently, we proposed a new transformation between the angle of canonical coordinates and the bond angle to describe the bending motion in Potential Energy Surfaces (PES) of bent triatomic molecules. In this work we extend the transformation to include linear triatomic molecules. Results for the linear triatomic molecule N₂O are reported.     

A procedure of determining potential energy surfaces of triatomic molecules from inversion of spectroscopic data

In this paper,we have suggested an iterative procedure of optimization of the linearparameters in an analytic potential energy function for a triatomic molecule,by combining both variational and second order perturbation methods.The most important feature of this procedure is that the objective function is an analytical expression which can be optimized easily.The application to the water molecule is presented.     

双原子分子振动对热力学性质的影响

本文在分析了双原子分子振动能级的完备性和有限性及其对统计计算带来的影响的基础上,借助代数（AM）方法得到的双原子分子振动能级完全集合,采用量子力学统计系综方法,讨论了双原子分子振动能量对宏观热力学性质的统计贡献,并以氮气为例计算了相应的热力学函数和振动热容量．结果表明,真实的双原子分子振动能级是有限的;确定最高振动量子数和振动能级完全集合是正确进行统计分析的基础和关键;考虑振动能级的完备性和有限性后,只能导致数值解而不是解析解,所得的结果优于谐振子模型的解析结果,与实验数据吻合得很好．     

Charge fluctuations and correlation strength in chemical bonds: First-row homonuclear diatomic molecules

We investigate, by means of ab initio calculations, the strength of electron correlations within covalent bonds: the first-row homonuclear diatomics serve as test cases. As an appropriate measure of the correlation strength, we introduce the reduction of the mean-square deviations of the electronic charges in localized orbitals forming a bond. A recently developed population analysis in terms of local operators derived from localized molecular orbitals is thereby used. The correlation-strength parameter depends only weakly on dynamical correlations as test calculations demonstrate. Therefore, the full-valence complete active space self-consistent field (CASSCF) approximation is applied in order to study the changes in the correlation strength with changing bond length for different types of bonds. A number of simple rules emerge from this discussion. In addition, we show that charge fluctuations are not only a reliable measure of intrabond correlation effects, but also can be used to monitor intraatomic quasi-degeneracy effects as well as the interdependence within multiple bonds. © 1998 John Wiley & Sons, Inc. Int J Quant Chem 67: 157–173, 1998     

Studies on the full vibrational energies and dissociation energies of some heteronuclear diatomic molecules

A parameter-free analytical formula for dissociation energies of diatomic molecules is proposed by Fan and Sun (2009) [20] based on LeRoy and Bernstein's vibrational energy expression near dissociation limit. Using three highest vibrational energies which may be generated by the algebraic method (AM) presented in our previous study and by some other physical methods, the new formula is applied to study the molecular dissociation energies of 10 electronic states of KH, ⁷LiD, ⁷LiH, ⁶LiH, NaK, NaLI and NaRb heteronuclear diatomic molecules which have regular (Morse-like) potentials in this work. The results show that the AM energies and dissociation energies have excellent agreement with experimental values.     

Accurate electron affinities of several diatomic and triatomic molecules

The electron affinity of several diatomic and triatomic molecules is computed with an error of less than 0.1 eV using the second-order Møller-Plesset method and a 6.311 + G(2d,2p) basis set. The importance of the zero-point energy correction is tested and a comparison with the results obtained with other basis sets is made.