COLLABORATIVE RESEARCH: NANOMESO: A NSF-EC Cooperative Activity in Computational Research to Study Nano/Meso Length Scale Effects on Crystal Plasticity

本合作奖是对提交给NSF-EC计算材料研究合作活动的提案的回应。该项目涉及美国俄亥俄州立大学、斯坦福大学和洛斯阿拉莫斯国家实验室，以及瑞士、德国和荷兰的合作机构。这项合作活动的目的是开发和验证一种计算方法，以理解和预测纳米和亚微米尺度上独特的塑性现象。近年来，合成、表征和计算技术的进步揭示了传统晶体塑性理论甚至最近的应变梯度理论无法解释的惊人塑性现象。这些现象与样品尺寸缩小到亚微米级和结构长度尺度（如晶粒尺寸）减小到纳米级有关。一个令人兴奋的前景是，新的变形机制已经确定，如果理解，可以使材料的发展具有无与伦比的强度。因此，所提出的工作的主要影响是对材料强度在长度尺度上的理解，而不是目前塑性理论所解决的。这样的活动预计会影响我们对薄膜强度和加工硬化的理解，并指导我们对MEMS中使用的小型器件的适当材料参数的理解。该项目的高智力价值源于解决亚微米和纳米尺度样品所带来的可塑性的基本性质的目标，以及利用从头算、原子论和Peierls方法计算材料科学的创造性过程，以支持位错动力学水平建模与新型微柱和原位x射线衍射验证技术之间的直接比较。当前塑性理论的不足之处，包括应变梯度公式，将通过一个系统的方法来解决，其中交叉滑移动力学和自由表面和晶界作为源和汇的作用将被系统地研究。这项研究的一个令人兴奋的前提是，亚微米和纳米尺度的样品可能从“错位饥饿”中获得非凡的强度。一个主要的结果是，几种计算技术之间的相互作用将为亚微米和纳米级组件的新塑性理论提供基础。该项目的广泛影响来自于当前的工业和科学推动力，以了解小型设备的特性。该研究旨在通过提供一个计算工具基础来预测部件的机械性能，从而实现小型机械设备的设计和开发，因为尺寸和结构被缩小到亚微米和纳米尺度。我们的计算和实验结果将被打包到一个开放的网站上，供学术界和工业界使用，特别是美国和欧盟的学术界和工业界使用，并将为亚微米尺度上全面、可访问的计算材料结果树立一个先例。致力于参与代表性不足群体的研究人员、国际合作提供的独特教育交流以及拟议的一系列基于网络的讲座来教授本项目中使用的每种计算材料方法的基础，将增强教育影响。该合作奖是对提交给NSF-EC计算材料研究合作活动的提案的回应。该项目涉及美国俄亥俄州立大学、斯坦福大学和洛斯阿拉莫斯国家实验室，以及瑞士、德国和荷兰的合作机构。这项合作活动的目的是开发和验证一种计算方法，以理解和预测纳米和亚微米尺度上独特的塑性现象。近年来，合成、表征和计算技术的进步揭示了传统晶体塑性理论甚至最近的应变梯度理论无法解释的惊人塑性现象。这些现象与样品尺寸缩小到亚微米级和结构长度尺度（如晶粒尺寸）减小到纳米级有关。一个令人兴奋的前景是，新的变形机制已经确定，如果理解，可以使材料的发展具有无与伦比的强度。因此，所提出的工作的主要影响是对材料强度在长度尺度上的理解，而不是目前塑性理论所解决的。这样的活动预计会影响我们对薄膜强度和加工硬化的理解，并指导我们对MEMS中使用的小型器件的适当材料参数的理解。该项目的高智力价值源于解决亚微米和纳米尺度样品所带来的可塑性的基本性质的目标，以及利用从头算、原子论和Peierls方法计算材料科学的创造性过程，以支持位错动力学水平建模与新型微柱和原位x射线衍射验证技术之间的直接比较。当前塑性理论的不足之处，包括应变梯度公式，将通过一个系统的方法来解决，其中交叉滑移动力学和自由表面和晶界作为源和汇的作用将被系统地研究。这项研究的一个令人兴奋的前提是，亚微米和纳米尺度的样品可能从“错位饥饿”中获得非凡的强度。一个主要的结果是，几种计算技术之间的相互作用将为亚微米和纳米级组件的新塑性理论提供基础。该项目的广泛影响来自于当前的工业和科学推动力，以了解小型设备的特性。该研究旨在通过提供一个计算工具基础来预测部件的机械性能，从而实现小型机械设备的设计和开发，因为尺寸和结构被缩小到亚微米和纳米尺度。我们的计算和实验结果将被打包到一个开放的网站上，供学术界和工业界使用，特别是美国和欧盟的学术界和工业界使用，并将为亚微米尺度上全面、可访问的计算材料结果树立一个先例。致力于参与代表性不足群体的研究人员、国际合作提供的独特教育交流以及拟议的一系列基于网络的讲座来教授本项目中使用的每种计算材料方法的基础，将增强教育影响。

TECHNICAL EXPLANATION This collaborative award is made in response to proposals submitted to the FY05 NSF-EC Cooperative Activity in Computational Materials Research. The project involves the Ohio State University, Stanford University and Los Alamos National Laboratory in the US and collaborating institutions in Switzerland, Germany and the Netherlands. The aim of this cooperative activity is to develop and validate a computational approach to understand and predict unique plasticity phenomena at the nano and sub-micron scales. In recent years, a combination of advances in synthesis, characterization, and computational techniques has revealed striking plasticity phenomena that are not explained by traditional crystal plasticity theories or even more recent strain gradient theories. These phenomena are associated with shrinking sample size to the sub-micron regime and decreasing structural length scales such as grain size to the nano-scale regime. An exciting prospect is that new deformation regimes have been identified which, if understood, could enable the development of materials with unrivaled strength. Thus, the primary impact of the proposed work is an understanding of material strength at length scales not addressed by current plasticity theories. Such an activity is expected to impact our understanding of strength and work hardening in thin films and guide our understanding of appropriate material parameters for small-scale devices used in MEMS.The high intellectual merit of this project derives from a goal to address the fundamental nature of plasticity posed by sub-micron and nano-scale samples, and from the creative process by which ab initio, atomistic, and Peierls approaches to computational materials science are used to support a direct comparison between dislocation dynamics level modeling and novel micro-pillar and in-situ x-ray diffraction verification techniques. The inadequacies of current plasticity theories, including strain gradient formulations, will be addressed via a systematic approach in which the kinetics of cross slip and role of free surfaces and grain boundaries as sources and sinks will be systematically studied. An exciting premise in this investigation is that sub-micron and nano-scale samples may derive extraordinary strength from "dislocation-starvation." A principle outcome is that the proposed, focused interaction among several computational techniques will provide the basis for a new plasticity theory for sub-micron and nano-scale components.The broader impact of the project draws from the current industrial and scientific thrusts to understand the properties of small devices. The research is aimed at enabling small mechanical device design and development, by providing a computational tool base with which to predict the mechanical properties of components as size and structure are diminished to the sub-micron and nano-scale. Our computational and experimental findings will be packaged into an open web site for use by the academic and industrial communities - particularly those in the US and EC - and will set a precedent for comprehensive, accessible computational materials results at the sub-micron scale.The educational impact will be enhanced by investigators who are commited to participation from under-represented groups, the unique educational exchange offered by an international collaboration, and a proposed series of web-based lectures to teach the basis of each of the computational materials methods to be used in this program.NON-TECHNICAL EXPLANATIONThis collaborative award is made in response to proposals submitted to the FY05 NSF-EC Cooperative Activity in Computational Materials Research. The project involves the Ohio State University, Stanford University and Los Alamos National Laboratory in the US and collaborating institutions in Switzerland, Germany and the Netherlands. The aim of this cooperative activity is to develop and validate a computational approach to understand and predict unique plasticity phenomena at the nano and sub-micron scales. In recent years, a combination of advances in synthesis, characterization, and computational techniques has revealed striking plasticity phenomena that are not explained by traditional crystal plasticity theories or even more recent strain gradient theories. These phenomena are associated with shrinking sample size to the sub-micron regime and decreasing structural length scales such as grain size to the nano-scale regime. An exciting prospect is that new deformation regimes have been identified which, if understood, could enable the development of materials with unrivaled strength. Thus, the primary impact of the proposed work is an understanding of material strength at length scales not addressed by current plasticity theories. Such an activity is expected to impact our understanding of strength and work hardening in thin films and guide our understanding of appropriate material parameters for small-scale devices used in MEMS.The high intellectual merit of this project derives from a goal to address the fundamental nature of plasticity posed by sub-micron and nano-scale samples, and from the creative process by which ab initio, atomistic, and Peierls approaches to computational materials science are used to support a direct comparison between dislocation dynamics level modeling and novel micro-pillar and in-situ x-ray diffraction verification techniques. The inadequacies of current plasticity theories, including strain gradient formulations, will be addressed via a systematic approach in which the kinetics of cross slip and role of free surfaces and grain boundaries as sources and sinks will be systematically studied. An exciting premise in this investigation is that sub-micron and nano-scale samples may derive extraordinary strength from "dislocation-starvation." A principle outcome is that the proposed, focused interaction among several computational techniques will provide the basis for a new plasticity theory for sub-micron and nano-scale components.The broader impact of the project draws from the current industrial and scientific thrusts to understand the properties of small devices. The research is aimed at enabling small mechanical device design and development, by providing a computational tool base with which to predict the mechanical properties of components as size and structure are diminished to the sub-micron and nano-scale. Our computational and experimental findings will be packaged into an open web site for use by the academic and industrial communities - particularly those in the US and EC - and will set a precedent for comprehensive, accessible computational materials results at the sub-micron scale.The educational impact will be enhanced by investigators who are commited to participation from under-represented groups, the unique educational exchange offered by an international collaboration, and a proposed series of web-based lectures to teach the basis of each of the computational materials methods to be used in this program.