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, Martinus
• 金额: $ 4.66万
• 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: 2018
• 资助国家: 加拿大
• 起止时间: 2018-01-01 至 2019-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=661025
• 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 long–range 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.

微观特性的计算机模拟是设计和理解新材料的关键，拟议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，这可以在未来由我们或其他团体在加拿大或其他地方大大扩展。在过去的十年里，在发展高精度、系统性和高效的基于波函数的分子体系量子化学方法方面取得了重大进展。一个主要的创新是本地相关耦合集群方法的发展，使用一个非常紧凑的表示，使用所谓的对自然轨道（PNOs）。虽然分子系统的计算是准确的，通用的和有效的，这是目前不正确的周期性固体。密度泛函理论，通常与平面波和赝势结合使用，是最广泛使用的，但这样的计算固体几乎不准确或可靠的波函数方法用于分子。在这个提议中，目的是将分子的已证明的方法推广到周期性固体的领域，直到完全的三维晶体。我们的策略的新奇是使用平移对称性结合当地PNO相关的方法，在完全类似的分子系统。关键思想是定义一组反映系统对称性/周期性的局部占据轨道，但通常是线性相关的。这种新方法需要对传统方法进行重大修改（已在分子的试点实施中进行了部分测试）。一个新的自动代码生成器将被开发，这将大大促进有效的计算机实现。** 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，平面波技术的使用已被证明特别有效。因此，在第二条研究线中，我们计划通过将全部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佳部分。短程部分由直接空间（类分子）技术处理，而长程部分在紧凑的倒易空间中使用傅里叶变换（即平面波）处理。** 通过合理地结合两个世界的优点，我们预计我们可以开发一个基于波函数的计算机程序来计算固态系统的结构，能量学，材料和光谱特性，其准确性和效率与最先进的分子代码相同。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顺利实施，并将为学生提供非常高水平的培训。