Atomistic Simulation Investigation on Processing-Structure-Property Relation of Magnetic Metal Alloy Nanostructures

非技术综述：磁性金属合金纳米结构在生物医学诊断、药物输送、催化、机械驱动和超高密度记录等领域有着广泛的应用。该项目将在新型磁性金属合金纳米结构的合理设计领域产生和传播新的计算技术和基础知识。该项目预计将影响材料科学、物理、化学、生物学、医疗健康和计算机技术等科学领域。该项目的成果将包括有关纳米材料加工和晶体结构如何共同决定合金纳米结构的磁性的知识，以及使用计算技术进行材料设计的能力。为了最大限度地扩大该项目对更广泛社区的影响，PI将把研究成果纳入课程改进、学生培训、产业合作和K-12推广计划。参与该项目的学生将获得计算材料科学方面的高级专业知识。特别是，PI将利用这一项目的教育活动来激发不同种族背景的高中生对理工科学科的兴趣。技术摘要：从当代多晶介质(由几十或数百个颗粒组成)转换为每比特一个单晶磁性纳米结构将大大减少信息档案的体积和访问时间。为了实现这一纳米技术，本项目的目标是准确预测磁性金属合金纳米结构的表面偏析、原子有序性和磁性，并进一步加深对这些磁性合金纳米结构加工-结构-性能关系的基本理解。提出的研究活动包括模拟一些选定的二元和三元磁性合金纳米结构的表面偏析过程，分析原子有序性随合金纳米结构的尺寸、形状、组成和加工条件的变化，预测合金纳米结构及其热力学平衡结构的磁性，以及利用计算技术阐述合金纳米结构的表面偏析、原子有序性和磁性之间的交织关系。原子蒙特卡罗模拟将用于获得合金纳米结构的热力学平衡构型，第一性原理密度泛函理论计算将用于预测合金纳米结构的磁性。这项工作将为通过调整磁性合金纳米结构的成分、结构和加工条件来优化其性能提供知识。因此，这项研究将增强我们的能力和丰富我们的知识，开发良好控制的磁性金属合金纳米结构，以促进超高密度记录技术的发展。

NON-TECHNICAL SUMMARY:Magnetic metal alloy nanostructures have wide applications in the fields of biomedical diagnostics, drug delivery, catalysis, mechanical actuations, and ultra-high density recording. This project will produce and disseminate new computational techniques and basic knowledge in the area of rational design of novel magnetic metal alloy nanostructures. The project is expected to impact scientific areas of materials science, physics, chemistry, biology, medical health, and computer technology. The outcomes of the project will comprise knowledge on how nanomaterial processing and crystal structure collectively determines the magnetic properties of alloy nanostructures as well as the capability to employ computation techniques for material design. To maximize the impact of the project to the broader community, the PI will incorporate the research results into curriculum enhancement, student training, industrial collaboration, and K-12 outreach program. The students involved in the project will gain advanced expertise in computational materials science. In particular, the PI will use the educational activity of this project to inspire the interests of high school students with diverse ethnic backgrounds in science and engineering disciplines.TECHNICAL SUMMARY:Switching from contemporary polycrystalline media (consisting of dozens or hundreds of grains per bit) to one single crystalline magnetic nanostructure per bit will significantly decrease the volume and accessing time for information archive. To enable this nanotechnology, the objective of this project is to accurately predict the surface segregation, atomic ordering, and magnetic properties of magnetic metal alloy nanostructures and further advance the fundamental understanding of the processing-structure-property relation for these magnetic alloy nanostructures. The proposed research activities include simulating the surface segregation process in some selected binary and ternary magnetic alloy nanostructures, analyzing the variation of atomic ordering as a function of the size, shape, composition, and processing conditions of the alloy nanostructures, predicting the magnetic properties of the alloy nanostructures with their thermodynamically equilibrated structures, and elaborating the interweaved relation among surface segregation, atomic ordering, and magnetic property of the alloy nanostructures using computational techniques. Atomistic Monte Carlo simulations will be performed to acquire the thermodynamically equilibrated configurations of the alloy nanostructures and the first-principles density functional theory calculations will be used to predict the magnetic properties of the alloy nanostructures. This work will provide knowledge for performance optimization of magnetic alloy nanostructures through tuning their composition, structure, and processing conditions. Therefore, the proposed research will strengthen our capability and enrich our knowledge in developing well-controlled magnetic metal alloy nanostructures for advancing ultra-high density recording technique.