Materials World Network: Computer-based discovery of novel low-energy structures in intermetallic compounds

金属间化合物可以以各种晶体结构存在。粗略地说，2N结构可以由具有N个晶格位置的二元A1-xBx系统制成。结构决定了延展性、硬度和导电性等性能。然而，许多金属间化合物的结构是未知的实验。这一建议提供了一个理论方法，预测稳定的晶体结构，为一个给定的化合物从第一性原理。特别是，我们关注的是在非理想的化学计量和其他技术的发展，以研究这些系统的不同的金属间化合物的研究。我们将结合现代统计力学基态搜索技术使用混合基簇扩展，并预测迄今为止尚未通过实验确定的金属间化合物的稳定结构。这将包括：（a）CuPd和CuMn的一维和二维结构-这些是表现出一维和二维周期性的神秘结构。（B）早期过渡金属氮化物和碳化物中空位的有序化。在这些系统中，空位形成特殊的空间排列。（c）确定Mo-Ta和Nb-W的基本相行为。这些材料系统的研究还需要开发新的方法：1。发展新的动力学-蒙特卡罗程序来研究微结构的演化。2.确定合金系统基态的“遗传算法”方法的发展。3.开发处理BCC基合金的混合基簇扩展代码该项目的更广泛影响包括：1.研究系统是广泛材料类别的原型，从这些系统中获得的知识将有助于我们对广泛材料的理解。2.开发研究合金的工具，供其他研究人员免费使用。3.为本科生，特别是那些来自物理学和材料科学代表性不足的人口群体的学生，提供研究经验和一对一的教师指导。G.哈特目前正在指导三名本科生，其中包括两名女性，一名是美国土著。4.培训学生UNIX操作系统，执行计算代码，脚本和编程，以及其他对学生有用的通用计算机技能。5.学生的长期参与，从项目开始到最终出版。建议的协作结合了三个群体的力量：（1）A的NREL群体; Zunger（NSF的免费PI），最初开发了混合基集群扩展，并已应用于许多系统。该小组在合金理论方面处于世界领先地位已有20年。(2)S. Müller在埃尔兰根德国，特别注意到其在材料的低维方面的兴趣。(3)G.哈特是北方亚利桑那大学（NAU）的新教员。该小组以其在研究空缺排序化合物方面的经验而闻名，正在为本科生提供从事重大项目的研究经验，特别是美洲原住民，西班牙裔和女性。

Intermetallic compounds can exist in a variety of crystal structures. Roughly, 2N structures can be made from a binary A1-xBx system with N lattice sites. The structure determines properties such as ductility, hardness, and conductivity. Yet the structure of many intermetallics is unknown experimentally. This proposal offers a theoretical methodology for predicting the stable crystal structures for a given compound from first principles. In particular, we are concerned with the study of different intermetallic compounds at non-ideal stoichiometries and the development of additional techniques to study such systems. We will use the Mixed-Basis Cluster Expansion in conjunction with modern statistical mechanics ground state search techniques and predict the stable structures for intermetallics that have so far eluded experimental determination. This will include: (a) one- and two-dimensional structures of CuPd and CuMn-these are mysterious structures that exhibit one- and two-dimensional periodicities, (b) ordering of vacancies in early transition metal nitrides and carbides. In these systems, the vacancies form peculiar spatial arrangements, (c) determination of the fundamental phase behaviour of Mo-Ta and Nb-W. The study of these material systems also requires development of new methodologies: 1. Development of new kinetic-Monte Carlo codes to study evolution of microstructures. 2. Development of a "genetic algorithm" approach to determining ground states in alloy systems. 3. Development of mixed-basis cluster expansion codes that handle BCC-based alloys The broader impacts of the project include: 1. Systems of study are archetypes in broad classes of materials and the knowledge gained for these systems will aid in our understanding of a broad range of materials. 2. Development of tools for studying alloys that will be freely available to other reseachers. 3. Provide undergraduate students, especially those from demographic groups underrepresented in physics and materials science, with research experience and one-to-one faculty mentoring. G. Hart is currently mentoring three undergraduate students, including two women, one a native American. 4. Train students in UNIX operating system, executing computional codes, scripting & programming, and other general computer skills that will be useful to students. 5. Long term involvement of the students, from project inception to final publication. The proposed collobaration combines the strength of three groups: (1) the NREL group of A. Zunger (a no-cost PI to NSF) where the mixed-basis cluster expansion was originally developed and has been applied to many systems. This group has been a world leader in the theory of alloys for 20 years. (2) The new research group of S. Müller in Erlangen Germany, particularly noted for its interest in low-dimensional aspects of materials. (3) The new research group of G. Hart, a new faculty member at Northern Arizona University (NAU). This group, noted for its experience in studying vacancy ordering compounds, is providing undergraduates with research experience working on significant projects, particularly native Americans, Hispanics, and women.