Ex nihilo crystal structure discovery

从无到有的晶体结构发现

• 批准号: EP/G007489/1
• 负责人: Christopher Pickard
• 金额: $ 173.33万
• 依托单位: University of St Andrews
• 依托单位国家: 英国
• 项目类别: Fellowship
• 财政年份: 2008
• 资助国家: 英国
• 起止时间: 2008 至 无数据
• 项目状态: 已结题
• 来源: https://gtr.ukri.org/projects?ref=EP%2FG007489%2F1
• 关键词: Ex; nihilo; crystal; structure; discovery

The discovery that matter is made up of atoms ranks as one ofmankind's greatest achievements. Twenty first century science isdominated by a quest for the mastery (both in terms of control andunderstanding) of our environment at the atomic level.In biology, understanding life (preserving it, or even attempting tocreate it) revolves around large, complex, molecules -- RNA, DNA, andproteins.Global warming is dictated by the particular way atoms are arrangedto make small greenhouse gas molecules, carbon dioxide and so on.The drive for faster, more efficient, cheaper computer chips forcesnanotechnology upon us. As the transistors that make up themicroscopic circuits are packed ever closer together, electronicengineers must understand where the atoms are placed, or misplaced, inthe semiconducting and insulating materials.Astronomers are currently, daily, discovering new planets outside oursolar system, orbiting alien stars. The largest are the easiest tospot, and many are far larger than Jupiter. The more massive theplanet the higher pressures endured by the matter that makes up itsbulk. How can we hope to determine the structure of matter at theseconditions?The atomic theory of matter leads to quantum mechanics -- a mechanicsof the every small. In principle, to understand and predict thebehaviour of matter at the atomic scale simply requires the solutionof the quantum mechanical Schroedinger equations. This is a challengein itself, but in an approximate way it is now possible to quicklycompute the energies and properties of fairly large collections ofatoms. But is it possible to predict how those atoms will be arrangedin Nature - ex nihilo, from nothing but our understanding ofphysics?Some have referred to it as a scandal that the physical sciencescannot routinely predict the structure of even simple crystals -- butmost have assumed it to be a very difficult problem. A minimum energymust be found in a many dimensional space of all the possiblestructures. Those researchers brave enough to tackle this challengehave done so by reaching for complex algorithms -- such as geneticalgorithms, which appeal to evolution to breed ever betterstructures (with better taken to mean more stable). However, Ihave discovered to my surprise, and to others', that the very simplestalgorithm -- throw the collection of atoms into a box, and move theatoms downhill on the energy landscape -- is remarkably effectiveif it is repeated many times.This approach needs no prior knowledge of chemistry. Indeed thescientist is taught chemistry by its results -- this is critical ifthe method is to be used to predict the behaviour of matter underextreme conditions, where learned intuition will typically fail.I have used this approach, which I call random structure searching to predict the structure of crystals ex nihilo. My firstapplication of it has been to silane at very high pressures, and thestructure I predicted has recently been seen in experiments. Butprobably the most impressive application so far has been to predictingthe structure of hydrogen at the huge pressures found in the gas giantplanets, where it may be a room temperature superconductor.In the course of my fellowship I will extend this work to try toanticipate the structure of matter in the newly discovered exoplanets,to try to discover and design materials with extreme (and hopefully,extremely useful) properties, and to help pharmaceutical researchersunderstand the many forms that their drug molecules adopt when theycrystallise.

物质是由原子组成的这一发现被列为人类最伟大的成就之一。21世纪的科学被一种对掌握在原子水平上对我们的环境的控制和理解。在生物学中，（保存它，甚至试图创造它）都围绕着大而复杂的分子-- RNA、DNA和蛋白质。全球变暖是由原子被吸收成小的温室气体分子的特殊方式决定的，对更快、更有效、更便宜的计算机芯片的追求迫使我们采用纳米技术。随着构成微观电路的晶体管越来越紧密，电子工程师必须了解原子在半导体和绝缘材料中的位置或错位。目前，天文学家每天都在太阳系外发现新的行星，它们围绕着外星恒星运行。最大的是最容易被发现的，许多比木星大得多。行星的质量越大，构成其体积的物质所承受的压力就越大.在这种情况下，我们怎么能希望确定物质的结构呢？物质的原子论导致了量子力学--一种研究每一个微小事物的力学。原则上，要理解和预测物质在原子尺度上的行为，只需要解量子力学的薛定谔方程。这本身就是一个挑战，但现在可以用近似的方法快速计算相当大的原子集合的能量和性质。但是，仅仅从我们对物理学的理解，就有可能预测这些原子在自然界中是如何被发现的吗？有些人认为，物理科学甚至不能常规地预测简单晶体的结构是一个丑闻，但大多数人认为这是一个非常困难的问题。必须在所有可能结构的多维空间中找到最小能量。那些有足够勇气应对这一挑战的研究人员已经通过复杂的算法实现了这一目标--比如遗传算法，它呼吁进化来培育更好的结构（更好意味着更稳定）。然而，令我和其他人惊讶的是，我发现最简单的算法--把原子的集合扔进一个盒子里，然后把原子在能量图上向下移动--只要重复多次，就非常有效。这种方法不需要事先掌握化学知识。事实上，科学家是通过化学的结果来学习的--这是至关重要的，如果这种方法被用来预测物质在极端条件下的行为，在这种情况下，后天的直觉通常会失败。我已经使用了这种方法，我称之为随机结构搜索来预测晶体的结构。我的第一个应用是在高压下的硅烷，我预测的结构最近在实验中看到了。但迄今为止最令人印象深刻的应用可能是预测巨大气体行星中氢的结构，在那里它可能是一种室温超导体。在我的研究期间，我将把这项工作扩展到尝试预测新发现的系外行星中的物质结构，尝试发现和设计具有极端高温的材料。（希望是非常有用的）性质，并帮助制药研究人员了解他们的药物分子在结晶时所采用的多种形式。