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

基本信息

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

项目摘要

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、实施和使用一种无参数的量子力学模拟方法，以可承受的计算成本对分子特性进行化学精确描述。该方法基于相关能量的随机相位近似（RPA）。与之前的 RPA 方法相比，该新方法独立于传统的半局部密度泛函理论 (DFT)。新方法代表了 Kohn-Sham/Hartree-Fock 方案的推广，是准确描述弱化学键（例如长程色散相互作用）以及隔离器、半导体和类金属化合物中相关性的有前途的工具。使用RPA，能量包含完整的Fock交换和基于RPA的相关能量。与半局域 DFT 中的动能一样，交换和关联也用轨道表达式来表示。轨道构成了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相关 DFT 借用的高效线性响应技术来计算的。这与单参考后 Hartree-Fock 方法形成对比，后者利用属于电子激发到虚拟轨道的行列式。因此，RPA 是精确波函数技术和基于 DFT 的合理近似的结合。到目前为止，轨道是通过半局部 DFT 确定的。这些轨道不属于 RPA 能量超曲面的最小值。这使得在 RPA 水平上计算分子特性变得困难。因此，轨道应该从基于 RPA 的总能量的变化中得出。这是第一次，这将在这个拟议的项目中完成，并将产生一种称为轨道优化 RPA 的新方法。它将用于预测色散结合络合物、偶极结合阴离子以及有或没有吸附分子的金属簇的平衡结构和电子激发光谱。