CAREER: Extending the lattice stability framework in ab initio alloy thermodynamics

职业：扩展从头算合金热力学中的晶格稳定性框架

• 批准号: 0953378
• 负责人: Axel van de Walle
• 金额: $ 43.6万
• 依托单位: California Institute of Technology
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2010
• 资助国家: 美国
• 起止时间: 2010-07-15 至 2011-12-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0953378&HistoricalAwards=false
• 关键词: CAREER; Extending; lattice; stability; framework

TECHNICAL SUMMARYThe Division of Materials Research and the Office of Cyberinfrastructure contribute funding to this CAREER award. This award supports computational and theoretical research and education aimed at improving our ability to predict phase diagrams of solid state alloys, based upon first-principles quantum mechanical calculations, without relying on experimental input. This project provides a firm conceptual framework and associated algorithms to model phenomena that commonly occur in technologically-relevant alloys, but that the field of alloy theory is currently poorly equipped to handle. The research has two thrusts:1) Lattice instabilities. The well-established CALPHAD and cluster expansion formalisms are fundamentally based on the assumption that a set of well-defined lattices (e.g. bcc, fcc, hcp) remain at least metastable at all compositions. However, in numerous alloy systems (e.g. Ti-Al, Cu-Fe, etc.), some lattices are not even mechanically stable, thus impeding any attempts at calculating a proper free energy. This project handles this fundamental conceptual issue by suitably constraining the domain of integration traditionally employed to calculate free energies based on rigorous geometrical partitioning techniques, but without necessitating a full anharmonic treatment.2) Novel compound prediction. While powerful methods (e.g. the cluster expansion) exist to model alloy ordering phenomena on a common underlying lattice, this project devises complementary methods that are applicable when this assumption is violated (notably, in Lave phases, sigma phases, etc.). The idea is to decompose the energy of an alloy system as a sum of atom cluster contributions. The proposed algorithm then attempts to re-assemble the lowest energy clusters, using combinatorial techniques, in search of low-energy crystal structures.The proposed methods will be implemented in the PI's Alloy Theoretic Automated Toolkit (ATAT), a software package that already has an established user base. The educational components of this research activity include augmenting ATAT by a companion educational web site, which will provide tutorials and social networking tools focusing on thermodynamics and phase diagrams, as well as using ATAT in undergraduate and graduate classes to give students hands-on experience with materials design tools of the future. To promote diversity, this project will build upon the efforts of the MRSEC at Caltech in recruiting minority undergraduates from California State University, Los Angeles.NON-TECHNICAL SUMMARYThe Division of Materials Research and the Office of Cyberinfrastructure contribute funding to this CAREER award. This award supports computational and theoretical research aimed at improving our ability to predict "phase diagrams". Phase diagrams are often called the "road maps of materials science", as they indicate which compounds form as a function of temperature and pressure, when different chemical elements are alloyed, thus providing crucial guidance in material design. This project focuses on prediction methods based on quantum mechanical calculations, without necessitating experimental input, a capability that is essential to enable the discovery of truly novel materials. The project provides a firm conceptual framework and associated algorithms to model phenomena that commonly occur in technologically-relevant alloys, but that the field of alloy theory is currently poorly equipped to handle. The proposed methods will be implemented in the PI's Alloy Theoretic Automated Toolkit (ATAT), a software package that already has an established user base. The educational components of this research activity include augmenting ATAT by a companion educational web site, which will provide tutorials and social networking tools focusing on thermodynamics and phase diagrams, as well as using ATAT in undergraduate and graduate classes to give students hands-on experience with materials design tools of the future. To promote diversity, this project will build upon the efforts of the Materials Research Science and Engineering Center at Caltech in recruiting minority undergraduates from California State University, Los Angeles.

技术总结材料研究部和网络基础设施办公室为该职业奖提供了资金。该奖项支持计算和理论研究和教育，旨在提高我们基于第一原理量子机械计算的固态合金相图的能力，而无需依赖实验输入。该项目为建模与技术相关的合金中通常发生的现象提供了一个牢固的概念框架和相关算法，但是合金理论的领域目前无法处理。该研究有两个推力：1）晶格不稳定性。从根本上讲，建立的calphad和群集扩张形式基于以下假设：一组定义明确的晶格（例如BCC，FCC，HCP）至少在所有组成的所有组合中都至少稳定。但是，在许多合金系统（例如Ti-Al，Cu-Fe等）中，某些晶格甚至都不是机械稳定的，因此阻碍了计算适当的自由能的任何尝试。该项目通过适当地限制传统上用于根据严格的几何分区技术来计算自由能的整合领域来处理这个基本的概念问题，但不需要进行完整的非谐波处理。2）新的复合预测。 尽管存在强大的方法（例如，群集扩展）来对一个共同基础晶格建模合金排序现象，但该项目设计了违反此假设时适用的互补方法（尤其是在Lave阶段，Sigma阶段等）。这个想法是将合金系统的能量分解为原子簇贡献的总和。然后，提出的算法尝试使用组合技术来重新组装最低的能量簇，以寻找低能量的晶体结构。拟议的方法将在PI的合金理论自动化工具包（ATAT）中实现，该软件包已经具有既定的访问量。这项研究活动的教育组成部分包括增强伴侣教育网站的ATAT，该网站将提供关注热力学和相图的教程和社交网络工具，以及在本科和研究生课程中使用ATAT，以使学生提供未来材料设计工具的动手体验。为了促进多样性，该项目将基于加州理工学院MRSEC在加利福尼亚州立大学，洛杉矶招募少数族裔大学生的努力。该奖项支持计算和理论研究，旨在提高我们预测“相图”的能力。相图通常称为“材料科学的道路图”，因为它们指示哪种化合物形成是温度和压力的函数，当将不同的化学元素合成时，因此在材料设计中提供了重要的指导。该项目的重点是基于量子机械计算的预测方法，而无需实验输入，这对于能够发现真正新颖的材料至关重要。 该项目提供了一个牢固的概念框架和相关算法，以模拟与技术相关的合金中通常发生的现象，但是合金理论的领域目前无法处理。所提出的方法将在PI的合金理论自动化工具包（ATAT）中实现，该软件包已经拥有已建立的用户群。这项研究活动的教育组成部分包括增强伴侣教育网站的ATAT，该网站将提供关注热力学和相图的教程和社交网络工具，以及在本科和研究生课程中使用ATAT，以使学生提供未来材料设计工具的动手体验。为了促进多样性，该项目将基于加州理工学院材料研究科学与工程中心的努力，招募了来自洛杉矶加利福尼亚州立大学的少数群体本科生。