Multiscale simulations of plasticity and fracture: the atomic-scale mechanisms of hydrogen embrittlement in engineering alloys.

分子动力学(MD)和原子模拟有可能影响从纳米技术到药物设计再到下一代先进材料的各个领域。然而，MD的预测能力在几个方面都是有限的。两个最大的限制是可以研究的原子数量少得令人望而却步，以及许多重要的原子物种组合的准确原子间势的可获得性有限(有时完全缺乏)。这项研究致力于开发有助于克服这些障碍的方法、算法和工具。同时，我们将利用这些工具在纳米尺度上研究与材料机械失效相关的重要科学问题。这些问题对增强性能的材料的设计、我们对纳米结构的理解以及结构材料中断裂和失效的基本原理都有影响。当然，了解和预测裂缝对于工程来说是至关重要的。我们对这一过程的了解越准确、越可靠，我们就越有能力自信地设计出不会突然和灾难性地崩溃的轻质、长期使用的结构。这项研究的重点是应用原子尺度模型来促进我们对结构工程金属塑性和断裂基本方面的理解，特别是解决氢在使某些重要金属变得更脆方面所起的重要作用。例如，我们将讨论铝合金中的氢脆效应，以及氢化物(沉淀氢化合物)在锆合金断裂行为中的作用。研究方法将使用由PI的研究小组和其他研究人员开发的计算机模拟技术。例如，我们将使用多尺度方法来扩展能够以原子精度运行的模拟的大小。这是通过明智地选择使用完全原子化的描述来处理问题的哪些区域来实现的，这使得我们能够研究应力裂纹尖端周围原子的真实配置中的氢-铝相互作用。此外，我们还将使用计算方法来探索原子组态，并准确地确定与位错成核等关键过程相关的激活能。这些数据的准确知识对于任何旨在预测断裂韧性的更大规模的模型都是至关重要的。最后，该项目将利用并在最近的OpenKIM.org项目的基础上开发描述锆氢系统的新的准确模型。这将使我们能够研究裂纹和嵌入氢化物之间的复杂相互作用。

Molecular dynamics (MD) and atomistic simulations have the potential to impact areas ranging from nanotechnology, to drug design, to the next generation of advanced materials. However, the predictive capabilities of MD are limited in several ways. The two most significant limitations are the prohibitively small numbers of atoms that can be studied and the limited availability (or sometimes complete lack of availability) of accurate interatomic potentials for many important combinations of atomic species. This research pursues the development of methodologies, algorithms and tools that help to overcome these obstacles. At the same time, we will use these tools to study important scientific questions related to the mechanical failure of materials at the nanoscale. These questions have consequences for the design of materials with enhanced properties, for our understanding of nanostructures, and for the fundamentals of fracture and failure in structural materials. Understanding and predicting fracture is, of course, of fundamental importance to engineering. The more accurate and reliable our understanding of the process, the better equipped we are to confidently design lightweight, long-serving structures that will not fail suddenly and catastrophically. This research focusses on applying atomic scale models to advance our understanding of fundamental aspects of plasticity and fracture in structural engineering metals, specifically addressing the important role that hydrogen plays in making certain important metals more brittle. For example, we will address hydrogen embrittlement effects in aluminum alloys, and the role of hydrides (precipitated hydrogen compounds) in the fracture behaviour of zirconium alloys. The research methodology will use computer simulation techniques that have been developed by the PI's research group and other researchers. For example, we will use multiscale methods that extend the size of the simulation that can be run with atomistic accuracy. This is accomplished through judicious choice of which regions of the problem are treated using a fully atomistic description, allowing us to study hydrogen-aluminum interactions within realistic configurations of atoms around a stressed crack tip. As well, we will employ computational methods to explore atomic configurations and accurately determine the activation energy associated with key processes like dislocation nucleation. Accurate knowledge of such data is of fundamental importance to any larger scale models aiming to predict fracture toughness. Finally, the project will both utilize and build upon the recent openKIM.org project to develop new accurate models to describe the zirconium-hydrogen system. This will allow us to study the complex interactions between cracks and embedded hydrides.