Ab initio calculations of molecular properties using the orbital optimized random-phase approximation method

使用轨道优化随机相位近似方法从头计算分子性质

• 批准号: 218736468
• 负责人: Dr. Asbjörn Burow
• 金额: --
• 依托单位: Department of Chemistry
• 依托单位国家: 德国
• 项目类别: Research Fellowships
• 财政年份: 2012
• 资助国家: 德国
• 起止时间: 2011-12-31 至 2012-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/218736468?language=en
• 关键词: Ab; initio; calculations; molecular; properties

In this project, I will develop, implement, and use a parameter-free quantum mechanical simulation method with affordable computational cost for chemically accurate description of molecular properties. The method is based on the random phase approximation (RPA) for correlation energy. In contrast to previous RPA methods, the novel approach is independent of conventional semi-local density functional theory (DFT). The new method represents a generalization of the Kohn-Sham/Hartree-Fock scheme and is a promising tool for accurate description of weak chemical bonding, e.g., long-ranged dispersion interactions, and for correlation in isolators, semiconductors, and metal-like compounds. Using RPA, the energy contains the full Fock exchange and the RPA-based correlation energy. Like the kinetic energy in semi-local DFT, exchange and correlation are represented by orbital expressions. The orbitals construct the electron density of the molecular ground state. Within this framework the RPA correlation energy is calculated using efficient linear response techniques borrowed from time-dependent DFT. This is in contrast to single reference post-Hartree-Fock methods which make use of determinants belonging to electron excitations into virtual orbitals. Hence, RPA is a combination of exact wavefunction techniques and reasonable approximations based on DFT. So far, the orbitals are determined by semi-local DFT. These orbitals do not belong to the minimum of the RPA energy hypersurface. This makes calculations of molecular properties difficult at the RPA level. Thus, the orbitals should be derived from variation of the RPA-based total energy. For the first time, this will be done in this proposed project and will lead to a new method called orbital optimized RPA. It will be used to predict equilibrium structures and electronic excitation spectra of dispersion-bound complexes, dipole-bound anions, and metal clusters with and without adsorbed molecules.

在这个项目中，我将开发，实施和使用无参数的量子机械模拟方法，具有负担得起的计算成本，以化学准确地描述分子特性。该方法基于相关能量的随机相位近似（RPA）。与以前的RPA方法相反，这种新方法独立于常规半局部密度功能理论（DFT）。新方法代表了Kohn-Sham/Hartree-fock方案的概括，是一种有前途的工具，用于准确描述弱化学键合，例如长期散布的相互作用，以及在隔离器，半导体和金属样化合物中的相关性。使用RPA，能量包含完整的FOCK交换和基于RPA的相关能。像半本地DFT中的动能一样，交换和相关性也以轨道表达方式表示。轨道构建分子基态的电子密度。在此框架内，RPA相关能量是使用从时间依赖性DFT借用的有效线性响应技术计算的。这与单个参考后 - 哈特里 - 库克方法相反，后者使用属于电子激发的决定因素，用于虚拟轨道。因此，RPA是基于DFT的精确波函数技术和合理近似值的组合。到目前为止，轨道由半本地DFT确定。这些轨道不属于RPA能量超表面的最小值。这使得在RPA水平上难以计算分子特性。因此，轨道应源自基于RPA的总能量的变化。这将首次在此提议的项目中完成，并将导致一种称为Orbital优化RPA的新方法。它将用于预测分散络合物，偶极子结合阴离子和带有和不吸附分子的金属簇的平衡结构和电子激发光谱。