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

科学家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可能的“理论”。数学是理论的语言，当然在物理科学中是这样，在生物学中也越来越多。它不仅仅是一种描述性的语言-它是一种允许理论被操纵、改进甚至反驳的工具。方程被求解-已知量被用来发现未知。随着现代功能强大的计算机的出现，理论家们获得了一个新的工具。现在，计算机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。我是一名理论家，对理解“凝聚态物质”--或我们作为人类可能接触到的宇宙中的大多数“物质”--感兴趣。这包括半导体晶体和液晶，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，大多数物质由非常小的粒子组成的力学：电子、质子和中子。我们仍然相信可以解释我们周围大多数现象的方程式是50多年前写下的，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，我实际上在各种现实情况下解决了这些方程式，从发现是什么让钻石如此坚固，到理解蛋白质。我帮助开发了最先进的计算机程序：CASTEP，它可以用来计算非常大的原子集合的性质。我的研究的一个特点是，我专注于解决最基本、最广泛应用的量子力学方程，我能够在广泛的科学学科中回答相关问题。我目前(和计划中的未来)的大部分工作都是为了帮助科学家“看到”物质的原子结构。当我们用肉眼看到什么东西时，光线从物体上散射出来，被我们眼睛的晶状体聚焦，投射到视网膜上。这向我们的大脑发送了一系列信号，大脑不知何故进行了必要的计算，让我们弄清楚我们看到的是什么。当人们测量到原子时，情况就更加复杂了。必须使用波长更短的光(或粒子)，量子力学变得非常重要。散射光(例如。X射线)被衍射，我们看到一连串不是原子的斑点。我们的大脑不能直接解释这些模式，但在晶体衍射的定量理论的帮助下，我们能够分辨出原子的位置。核磁共振技术不是基于散射和衍射的。施加在样品上的磁场使电流上升，而电流又产生磁场。电流取决于电子在样品中的位置和它们在做什么，可以通过特殊的原子核来测量，这种原子核的行为就像微小的磁铁。然而，原子的位置和测量到的磁场之间的关系并不直接。在我的研究过程中，我正在发展一种磁共振的量化理论，它有可能使核磁共振成为一种直接观察原子的方法，就像X射线结晶学一样-而不需要生长大而完美的晶体。

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.