Theory of Molecular Interaction and Its Application to Studies of Molecular Clusters

分子相互作用理论及其在分子簇研究中的应用

基本信息

批准号：
20550018
负责人：
IWATA Suehiro
金额：
$ 2.41万
依托单位：
Toyota Physical & Chemical Research Institute
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
2008
资助国家：
日本
起止时间：
2008 至 2010
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-20550018/
关键词：
分子間相互作用分子軌道理論基底関数欠損誤差電子相関理論ファン・デア・ワールス力分散項希ガス原子間相互作用 counterpoise procedure ファン・デア・ワールス項量子化学理論水2量体水素結合電荷移動項ゲストーホスト重水素効果

项目摘要

To evaluate the molecular interaction energy by the ab initio (first principle) quantum chemical calculations, the error inherent to the basis set expansions has to be removed or to be avoided. The causes of the error are the inconsistency in the approximation for the isolated systems and for the composite system. In the molecular orbital (MO) based theory and in most of the density functional theory (DFT), the one-electron functions (orbitals) are expanded in terms of Gaussian functions. So one of causes in the inconsistency is related with the orbitals used; which can be called the Orbital Basis Inconsistency (OBI). In MO theory, the many-electron wave functions are described by a superposition of electron configurations, or by a linear combination of Slater determinants. Thus, the second cause of the inconsistency is Configuration Basis Inconsistency (CBI). Using the locally projected molecular orbital (LPMO), the 3rd order single excitation perturbation (3rdSPT) and the 2nd order double excitation perturbation theory (2ndDPT) are developed. The theory can avoid the OBI by determining the MO under the local condition and the CBI by restricting the electron configurations in the perturbation theory. The method is tested for many molecular clusters using various basis sets, and the calculated binding energies are compared with the published reference energies. The developed code is sufficiently efficient to study a large water clusters such as (H_2O)_25 with 3rdSPT/aug-cc-pVDZ and (H_2O)_6 with 3rdSPT+2ndDPT/aug-cc-pVTZ.

为了通过从头算（第一原理）量子化学计算来评估分子相互作用能，必须消除或避免基组展开固有的误差。误差的原因是孤立系统和复合系统的近似不一致。在基于分子轨道（MO）的理论和大多数密度泛函理论（DFT）中，单电子函数（轨道）以高斯函数的形式展开。因此，不一致的原因之一与所使用的轨道有关；这可以称为轨道基础不一致（OBI）。在 MO 理论中，多电子波函数由电子构型的叠加或 Slater 行列式的线性组合来描述。因此，不一致的第二个原因是配置基础不一致（CBI）。利用局部投影分子轨道（LPMO），发展了三阶单激发微扰理论（3rdSPT）和二阶双激发微扰理论（2ndDPT）。该理论可以通过确定局域条件下的MO来避免OBI，通过限制微扰理论中的电子构型来避免CBI。该方法使用不同的基组对许多分子簇进行了测试，并将计算出的结合能与已发表的参考能进行了比较。开发的代码足够有效地研究大型水簇，例如使用 3rdSPT/aug-cc-pVDZ 的 (H_2O)_25 和使用 3rdSPT+2ndDPT/aug-cc-pVTZ 的 (H_2O)_6。