Local correlation approaches for ground and excited states of periodic systems

周期系统基态和激发态的局部相关方法

• 批准号: RGPIN-2018-04187
• 负责人: Nooijen, Marcel
• 金额: $ 9.32万
• 依托单位: University of Waterloo
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2022
• 资助国家: 加拿大
• 起止时间: 2022-01-01 至 2023-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=748029
• 关键词: Local; correlation; approaches; ground; excited

Computer simulations of microscopic properties are key to the design and understanding of new materials, and the aim of the proposed research is to develop a new set of tools to perform accurate simulations for solids, which can be greatly expanded on in the future by us or other groups, in Canada or elsewhere.The past decade has seen major progress in the development of highly accurate, systematic, and efficient wave function based quantum chemistry methods for molecular systems. A major innovation has been the development of local correlation coupled cluster methods using a very compact representation using so-called pair natural orbitals (PNOs). While calculations for molecular systems are accurate, versatile and efficient, this is currently not true for periodic solids. Density functional theory, often in conjunction with plane waves and pseudo potentials are most widely used, but such calculations for solids are not nearly as accurate or reliable as wave function methods used for molecules. In this proposal the aim is to generalize the proven methodology for molecules to the domain of periodic solids, up to full 3-dimensional crystals. The novelty of our strategy is the use of translational symmetry in conjunction with local PNO correlation approaches, in complete analogy to molecular systems. The key idea is to define a set of localized occupied orbitals that reflect the symmetry/periodicity of the system, but which will in general be linear dependent. This new approach requires non-trivial modifications to conventional methodologies (that have been partially tested in a pilot implementation for molecules). A new automatic code generator will be developed and this will greatly facilitate effcicient computer implementations. The long-range part of the Coulomb potential plays an essential role for solids, in particularly for metals, and the use of plane wave techniques have been proven particularly effective. In a second line of research we therefore plan to consolidate the best parts of solid state and molecular calculations by partitioning the full Coulomb potential in a short-range and an essentially pure longrange part. The short-range part is treated by direct space (molecular-like) techniques, while the long-range part is treated in a compact reciprocal space, using Fourier transforms, i.e. plane waves. By judicially combining the best of both worlds we anticipate we can develop a wave function based computer program to calculate structure, energetics, material and spectroscopic properties of solid state systems at the same level of accuracy and efficiency as state-of-the-art molecular codes. The research is open-ended as the use of a code generator will enable smooth implementation of methodology that currently still lies in the future, and will provide very high level training for students.

微观性质的计算机模拟是设计和理解新材料的关键，这项研究的目的是开发一套新的工具来对固体进行准确的模拟，将来我们或其他小组可以在加拿大或其他地方大大扩展这一工具。在过去的十年里，分子系统的高精度、系统和高效的基于波函数的量子化学方法的发展取得了重大进展。一项主要的创新是开发了使用所谓的自然轨道对(PNO)的非常紧凑的表示的局部相关耦合星系团方法。虽然对分子体系的计算是准确、通用和高效的，但目前对周期固体却并非如此。密度泛函理论通常与平面波和赝势一起使用，但对固体的这种计算远不如对分子的波函数方法那样准确或可靠。在这项提案中，目的是将已证实的分子方法学推广到周期性固体领域，直至全三维晶体。我们策略的新奇之处在于将平移对称性与局部PNO关联方法结合使用，完全类似于分子系统。其核心思想是定义一组局域占据轨道，它们反映了系统的对称性/周期性，但通常是线性相关的。这一新方法需要对传统方法(已经在分子的试点实施中进行了部分测试)进行重大修改。将开发一种新的自动代码生成器，这将极大地促进高效的计算机实现。库仑势的长程部分对固体特别是金属起着至关重要的作用，而平面波技术的使用已被证明是特别有效的。因此，在第二条研究路线中，我们计划通过将完整的库仑势划分为短程和基本上纯的长程部分来巩固固态和分子计算的最好部分。短程部分用直接空间(类分子)技术处理，而长程部分用傅里叶变换，即平面波，在紧凑的互易空间中处理。通过司法结合两个领域的最好，我们预计我们可以开发一个基于波函数的计算机程序，以与最先进的分子代码相同的精度和效率计算固态系统的结构、能量、材料和光谱性质。这项研究是开放式的，因为使用代码生成器将使目前仍在未来的方法得以顺利实施，并将为学生提供非常高水平的培训。