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

分子动力学（MD）和原子模拟具有影响从纳米技术、药物设计到下一代先进材料等领域的潜力。然而，MD的预测能力在几个方面受到限制。两个最重要的限制是，可以研究的原子数量少得令人望而却步，以及对许多重要的原子种类组合，精确的原子间电位的可用性有限（有时完全没有可用性）。本研究追求有助于克服这些障碍的方法、算法和工具的发展。同时，我们将使用这些工具来研究与纳米尺度材料机械失效相关的重要科学问题。这些问题对增强材料性能的设计，对我们对纳米结构的理解，以及对结构材料断裂和失效的基本原理都有影响。当然，理解和预测裂缝对工程来说是至关重要的。我们对这一过程的理解越准确和可靠，我们就越有信心设计出轻量级、长期服务的结构，这些结构不会突然和灾难性地失效。本研究的重点是应用原子尺度模型来推进我们对结构工程金属塑性和断裂的基本方面的理解，特别是解决氢在使某些重要金属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（沉淀的氢化合物）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可以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描述来处理问题的哪些区域来实现的，这使我们能够在应力裂纹尖端周围的实际原子构型中研究氢-铝相互作用。此外，我们将采用计算方法来探索原子构型，并准确确定与位错成核等关键过程相关的活化能。准确了解这些数据对于任何旨在预测断裂韧性的更大规模模型都是至关重要的。最后，该项目将利用并建立在最近的openKIM.org项目的基础上，开发新的精确模型来描述锆氢系统。这将使我们能够研究裂缝和嵌入的氢化物之间复杂的相互作用。

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.