Ab-Initio Identification of Atoms in Molecules

分子中原子的从头开始识别

• 批准号: 9612188
• 负责人: Klaus Ruedenberg
• 金额: $ 15.3万
• 依托单位: Iowa State University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 1997
• 资助国家: 美国
• 起止时间: 1997-01-01 至 2001-12-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=9612188&HistoricalAwards=false
• 关键词: Ab; Initio; Identification; Atoms; Molecules

The Theoretical and Computational Chemistry program is supporting Prof. K. Ruedenberg at Iowa State University. The research to be carried out over the next two years will focus on the development of a new quantum chemical theory that will result in corresponding new computational chemistry codes. The objective is the quantitative determination of atoms in molecules within the framework of rigorous ab-initio theory, and the quantitative expression of binding energies in terms of interactions between such atoms. The deformed atoms are determined through their optimal wave functions in terms of orbitals restricted to the full-valence-space MCSCF molecular orbital space. Oriented quasiatomic orbitals, maximally involved in specific bonds and with unambiguous electron populations, are determined through a density matrix analysis. The binding energy appears as the sum of contributions due to intra-atomic promotion and inter-atomic non-bonded repulsion, electron sharing and charge transfer. The energy gain due to charge transfer is identified by determining the optimal molecular MCSCF wave function without charge transfer. The covalent energy gain is derived from the configurations representing electron migrations between atoms. The analysis applies to non-equilibrium as well as to equilibrium geometries and will be extended beyond the full valence space. Although for two centuries chemical experimentation has been effectively guided by the concept of molecules being built from atoms, major unsolved problems have persisted to this day regarding the theoretical foundation of this well established empirical model and it has not yet been quantified within the context of rigorous quantum mechanical calculations. This is because the atoms-in-molecules concept is, in fact, not a fundamental one in basic theory. Recently, the Ruedenberg research group has developed a new analysis that is able to identify atomic sub-units in rigorous molecular calculations. With the help of this theoretical approach, atoms, as well as the interactions between them, will be quantitatively determined in molecules. The method to be developed is expected to make the results of theoretical computations more useful for practical chemical work by relating them more directly to the intuitive reasoning of experimentalists.

理论和计算化学计划是支持教授。 K.鲁登伯格在爱荷华州州立大学。 拟开展的研究 在未来两年将专注于开发一种新的量子 化学理论，将导致相应的新的计算 化学代码 目的是定量测定 在严格的从头算理论框架内， 结合能的定量表达 这样的原子之间。 变形的原子是通过它们的 最佳波函数的轨道限制在 全价空间MCSCF分子轨道空间。定向准原子 轨道，最大限度地参与特定的键，并与明确的 通过密度矩阵分析确定电子布居。 结合能表现为由于以下因素的贡献之和： 原子内促进和原子间非键排斥，电子 共享和电荷转移。 由于电荷转移而产生的能量增益为 通过确定最佳分子MCSCF波函数来识别 没有电荷转移。 共价能量增益来自于 代表原子间电子迁移的构型。 的 分析适用于非平衡以及平衡的几何形状 并且将延伸到整个价空间之外。 尽管两个世纪以来，化学实验一直有效地 在分子由原子构成的概念的指导下，少校 至今仍有一些理论上的问题没有得到解决。 这是一个建立良好的经验模型的基础，它还没有 在严格的量子力学的背景下被量化 计算。 这是因为原子在分子中的概念， 事实上，这不是基本理论中的一个基本问题。最近，Ruedenberg 一个研究小组开发了一种新的分析方法， 严格分子计算中的原子亚单位。 的帮助下 这种理论方法，原子，以及相互作用之间 它们将在分子中定量测定。什么方法 预计开发的理论计算结果 对实际化学工作更有用，因为它们更直接地与 实验主义者的直觉推理