Relativistic Calculations of Solid-state NMR parameters

固态核磁共振参数的相对论计算

• 批准号: 2103521
• 金额: --
• 依托单位: University of Oxford
• 依托单位国家: 英国
• 项目类别: Studentship
• 财政年份: 2018
• 资助国家: 英国
• 起止时间: 2018 至 无数据
• 项目状态: 已结题
• 来源: https://gtr.ukri.org/projects?ref=studentship-2103521
• 关键词: Relativistic; Calculations; Solid; state; NMR

Solid-State Nuclear Magnetic Resonance (NMR) spectroscopy is a powerful experimental probe of structure and dynamics on an atomic scale. It has been widely applied to problems in chemistry, material science, biology, physics, and geology. However, there is no simple theorem which allows the measured NMR spectrum to be related to the underlying chemical structure. For simple organic molecules and certain crystal structures empirical rules have been found, but for more complex systems interpretation of the experimental spectra can be difficult and often ambiguous. First principles quantum mechanical calculations of NMR parameters have the potential to provide the vital missing link between NMR spectra and the underlying microscopic structure. This challenge has led to the development of the Gauge Including Projector Augmented Wave (GIPAW) method (http://www.gipaw.net) which enables NMR parameters to be calculated within the planewave-pseudopotential formalism of density functional theory (DFT). The translational symmetry found in crystalline materials is specifically included within this method, although it can also be applied to aperiodic materials using a supercell approach. The ability to predict from first-principles NMR parameters for solid-state systems has had a significant impact on the solid-state NMR community. Such calculations are often an integral part of any experimental solid-state NMR study. However, a major limitation is the poor description of compounds containing heavier elements (roughly speaking those beyond Tellurium). This applies not just to the heavy atom itself, but to any light atoms (H, C) directly bonded to the heavier atom (the so called 'heavy atom - light atom effect) The reason for this is a neglect of relativistic effects which become important for increasing atomic number. But simply the heavier the atom, the deeper the potential the inner electrons experience, and the faster their speed. For moderately heavy atoms the inner electrons travel at an appreciable fraction of the speed of light. While so-called scalar relativistic effects are sufficient in some situations, a full treatment including spin-orbit coupling is essential to predict phenomena such as the heavy atom - light atom effect. We have recently extended the CASTEP code to include spin-orbit coupling in the calculation of ground state properties. The aim of this project will be to apply this functionality to the calculation of NMR properties in solids - enabling the accurate prediction of NMR parameters across the periodic table. This will involve the development of new theoretical equations and their implementation into a parallel electronic structure code (CASTEP http://www.castep.org). Applications of the new methodology will be extensive - and include areas such as catalysis, geominerals and pharmaceuticals, with collaborations in both academia and industry.EPSRC Classification: Computational and Theoretical Chemistry.

固体核磁共振波谱是一种在原子尺度上研究结构和动力学的强有力的实验探头。它已被广泛应用于化学、材料科学、生物、物理和地质等领域的问题。然而，没有一个简单的定理可以让测量的核磁共振谱与潜在的化学结构相关。对于简单的有机分子和某些晶体结构，已经找到了经验规则，但对于更复杂的系统，对实验光谱的解释可能很困难，而且往往是模棱两可的。首先，核磁共振参数的量子力学计算有可能提供核磁共振光谱和基本微观结构之间重要的缺失环节。这一挑战导致了包括投影增广波(GIPAW)方法(http://www.gipaw.net))在内的量规的发展，该方法使核磁共振参数能够在密度泛函理论的平面波-赝势形式下计算。在晶体材料中发现的平移对称性特别包括在这种方法中，尽管它也可以应用于使用超晶胞方法的非周期材料。根据第一原理预测固态系统的核磁共振参数的能力已经对固态核磁共振社区产生了重大影响。这样的计算通常是任何实验固体核磁共振研究的组成部分。然而，一个主要的限制是对含有较重元素的化合物(粗略地说，那些超出碲元素的化合物)的描述很差。这不仅适用于重原子本身，而且适用于任何直接与较重原子成键的轻原子(H，C)(所谓的“重原子-轻原子效应”)。这是因为忽略了相对论效应，而相对论效应对增加原子序数变得重要。但简单地说，原子越重，内部电子经历的势就越深，速度就越快。对于中等重的原子，内部电子的运动速度相当于光速的一小部分。虽然所谓的标量相对论效应在某些情况下就足够了，但要预测重原子-轻原子效应等现象，包括自旋-轨道耦合在内的全面处理是必不可少的。我们最近扩展了CASTEP程序，在基态性质的计算中包括了自旋-轨道耦合。该项目的目标是将这一功能应用于固体核磁共振性质的计算，从而能够准确预测整个元素周期表中的核磁共振参数。这将涉及发展新的理论方程并将其应用到并行电子结构代码(CASTEP http://www.castep.org).新方法的应用将是广泛的-包括催化、地球矿物和制药等领域，与学术界和工业界的合作。EPSRC分类：计算和理论化学。