A new solid-state theory for the prediction of Nuclear Magnetic Resonance J-coupling constants

科学家们试图了解我们周围的世界，如果没有仔细的、经常令人惊讶的实验观察，现代科学将一事无成。但所有的科学家也都是理论家，因为他们试图理解他们的实验，发现解释所有已知事实的最简单的“理论”。数学是理论的语言，在物理科学中是如此，在生物学中也越来越多。它不仅仅是一种解释性的语言-它还是一种工具，允许理论被操纵、改进，甚至被推翻。方程被求解-已知的量被用来发现未知的量。随着现代强大的计算机的出现，理论家们获得了新的工具。计算机现在不仅可以完成许多数学任务，比如解非常复杂的方程，而且还可以处理传统数学家用铅笔和大量纸张很难或不可能处理的理论。我是一个理论家，对理解“凝聚态物质”--或者说宇宙中我们人类可能接触到的大多数“东西”--很感兴趣。这包括超导晶体和液晶，金属和超导体，可能在地球或其他行星深处发现的矿物，甚至是维持我们生命的分子。我的研究所依赖的基本理论是在20世纪初发现的-量子力学，一种关于组成大多数物质的非常小的粒子的力学：电子，质子和中子。我们仍然相信的方程解释了我们周围看到的大多数现象，这些方程是五十多年前写下来的，但不可能解决！利用理论上的进步，并热情地利用计算机和超级计算机，我实际上解决了这些方程，用于大量的现实情况，从发现什么使钻石如此坚固，到理解蛋白质。我帮助开发了一个最先进的计算机程序：CASTEP，它可以用来计算大量原子的性质。我的研究的一个特点是，集中精力解决最基本的，广泛适用的量子力学方程，我能够回答广泛的科学学科中的相关问题。我目前（和未来计划）的大部分工作旨在帮助科学家“看到”物质的原子结构。当我们用肉眼看东西时，光从物体散射，通过我们眼睛的透镜聚焦，然后福尔斯落在视网膜上。这就向我们的大脑发送了一系列信号，大脑以某种方式进行了必要的计算，使我们能够弄清楚我们看到了什么。当人们试图看到原子时，情况就复杂多了。必须使用更短波长的光（或粒子），量子力学变得非常重要。散射光（如X射线）被衍射，我们看到的不是原子的斑点图案。我们的大脑不能直接解释这些图案，但借助晶体衍射的定量理论，我们能够分辨出原子的位置。核磁共振（NMR）技术不是基于散射和衍射。施加在样品上的磁场会产生电流，电流又会产生磁场.这些电流取决于电子在样品中的位置和它们的作用，并且可以通过像微小磁铁一样的特殊原子核来测量。然而，原子的位置和测量的磁场之间的关系并不简单。在我的研究过程中，我正在发展一种磁共振的定量理论，这种理论有可能使核磁共振成为一种直接的方法，把原子看作X射线晶体学-而不需要生长大的完美晶体。

Scientists try to understand the world around us and modern sciencewould have got nowhere without careful, and often surprising,experimental observations. But all scientists are theorists as well,as they seek to understand their experiments, discovering the simplestpossible ``theory'' that explains all the known facts.Mathematics is the language of theory, certainly in the physicalsciences, and increasingly in biology. It is not just a descriptivelanguage --- it is a tool that allows the theories to be manipulated,improved, or even disproved. Equations are solved --- known quantitiesare used to discover the unknowns.With the advent of modern powerful computers theorists have gained anew tool. Not only can computers now do many mathematical tasks, suchas solving very complex equations, they can also manipulate theoriesthat would be very difficult or impossible for a traditionalmathematician to handle using a pencil and lots of paper.I am a theorist who is interested in understanding ``condensedmatter'' --- or most of the ``stuff'' in the universe that we, ashumans, are likely to be able to touch. This includes semiconductorcrystals and liquid crystals, metals and superconductors, mineralsthat might be found deep in the Earth or other planets, and evenmolecules that keep us alive.The fundamental theory that my research relies on was discovered inthe early 20th century --- Quantum Mechanics, a mechanics of the verysmall particles that most matter is made of: electrons, protons andneutrons. The equations that we still believe explain most of thephenomena that we can see around us were written down over fifty yearsago, but were impossible to solve!Using theoretical advances and enthusiastically making use ofcomputers and supercomputers, I actually solve these equations for avast range of realistic situations, from discovering what makesdiamond so strong, to understanding proteins. I have helped develop astate-of-the-art computer program: CASTEP, which can be used tocalculate the properties of very large collections of atoms.A feature of my research is that having concentrated on solving themost basic, and widely applicable quantum mechanical equations I amable to answer relevant questions in a wide range of scientificdisciplines. Much of my current (and proposed future) work aims at helpingscientist ``see'' the atomic structure of matter. When we seesomething with our naked eyes, light scatters from the object, isfocused by our eye's lens and falls onto the retina. This sends aflurry of signals to our brain, which somehow does the necessarycalculations to allow us to figure out what we are seeing. When peopletry to see atoms the situation is more complicated. Shorter wavelengthlight (or particles) have to be used, and quantum mechanics becomesimportant. The scattered light (eg. x-rays) is diffracted and we see apattern of spots which are not atoms. Our brains cannot directlyinterpret these patterns, but with the help of a quantitative theoryof diffraction from crystals we are able to sort out where the atomsare. The technique of Nuclear Magnetic Resonance (NMR) is not based onscattering and diffraction. A magnetic field applied to a sample setsup electric currents, which in turn produce magnetic fields. Thesecurrents depend of where the electrons are in the sample and what theyare doing, and can be measured by special atomic nuclei which behavelike tiny magnets. However, the relationship between where the atomsare and the measured magnetic field is not straightforward. In thecourse of my research I am developing a quantitative theory ofmagnetic resonance which has the potential to enable NMR to be asdirect a way to see atoms as x-ray crystallography --- without theneed to grow large perfect crystals.