Phase-Space Natural Orbital Functional Theory

计算化学不仅在所有化学领域，而且在分子生物学和纳米技术等领域，已经成为预测、确认和解释实验结果的重要工具。高质量、数学严谨和计算昂贵的计算提供了实验测量误差范围内的化学性质，但目前对大型系统是不可行的。因此，当研究诸如蛋白质、材料表面或分子系综的整体性质(例如，对于溶解在水中的化合物)，有必要使用更近似的计算化学方法。 目前用于大分子体系计算研究的近似方法是密度泛函理论(DFT)，因为它结合了精度和效率。不幸的是，DFT无法正确描述键的断裂或形成，以及过渡金属和激发态的一般现象，这些现象是理解化学的关键。最近的研究表明，许多DFT失效的基础是静态相关性。我建议发展一种新的基于自然轨道泛函理论(NOFT)的计算化学方法。NOFT的一个关键特征是自然轨道被部分电子占据，这有效地处理了DFT遇到的静态关联问题。我们将利用密度泛函的成功概念，在NOFT的框架内，设计一个通用的、准确的自然轨道泛函。我们将结合我们的泛函和最新的理论进步来计算大系统，以创建一种计算化学方法，能够为大而复杂的分子系统提供在实验精度范围内的结果。这种方法的发展将使计算和实验研究人员能够可靠地确定当前计算方法不适合的体系的分子结构、反应路径和其他感兴趣的性质。

Computational chemistry has become an important tool for predicting, confirming, and explaining experimental results in not only all fields of chemistry, but in areas such as molecular biology and nanotechnology. High quality, mathematically rigorous, and computationally expensive calculations provide chemical properties within the errors of experimental measurements, but are currently unfeasible for large systems. Therefore when studying systems such as proteins, surfaces of materials, or bulk properties of molecular ensembles (eg. compounds dissolved in water), it is necessary to employ more approximate computational chemistry methods. The current approximate method of choice for the computational study of large molecular systems is density functional theory (DFT), due to its combination of accuracy and efficiency. Unfortunately, DFT is unable to properly describe bond breaking or formation, as well as transition metals and excited states in general, phenomena that are key to understanding chemistry. Recent research has revealed that the basis of many DFT failures is static correlation. I propose to develop a new computational chemistry method based on natural orbital functional theory (NOFT). A key feature of NOFT is the occupation of the natural orbitals by fractions of electrons which effectively treats the static correlation problem encountered by DFT. We will make use of the successful concepts of DFT, within an NOFT framework, to design a universal and accurate natural orbital functional. We will combine our functional with the latest theoretical advances for calculations on large systems to create a computational chemistry method capable of providing results within experimental accuracy for large and complex molecular systems. The development of such a method will allow computational and experimental researchers to reliably determine molecular structures, reaction pathways, and other properties of interest of systems for which current computational methods are unsuitable.