Atomistic Theory and Computer Simulation of Grain Boundary Structure and Diffusion

晶界结构和扩散的原子理论和计算机模拟

• 批准号: 9753243
• 负责人: Diana Farkas
• 金额: $ 27万
• 依托单位: Virginia Polytechnic Institute and State University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 1998
• 资助国家: 美国
• 起止时间: 1998-05-15 至 2002-04-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=9753243&HistoricalAwards=false
• 关键词: Atomistic; Theory; Computer; Simulation; Grain

9753243 Farkas This project is aimed at theoretical investigations and computer simulations of point defects and grain boundaries, as well as diffusion in the lattice and along grain boundaries in ordered compounds. The focus of research will be the intermetallic compound NiAl. The project includes collaborations with groups working on ab initio calculations and on diffusion experiments. Atomic structure and diffusion along grain boundaries in intermetallic compounds are of great interest in connection with their limited ductility and high-temperature creep resistance. Grain boundary diffusion in NiAl has never been studied experimentally or theoretically. Moreover, correct atomistic calculations of grain boundary diffusion coefficients have only become possible recently due to work done by the proposers on the jump correlation theory and the development of the respective simulation methods. These theory and simulation techniques will be further improved and applied to grain boundaries in NiAl. Angular-dependent semi-empirical potentials of the embedded- atom type will be developed for NiAl by fitting to both experimental properties and to the results of ab initio calculations. The atomic structure for 001 and 011 symmetrical tilt grain boundaries will be calculated using molecular statics and dynamics. The formation energies and equilibrium concentrations of point defects in the lattice and in the grain boundaries will be calculated. The atomic migration energies by different mechanisms in the lattice and in the grain boundary cores will also be calculated. The point defect concentrations and migration energies obtained will be used for the calculation of lattice and grain boundary diffusion coefficients of Ni and Al using novel methods of jump correlation theory and the Monte Carlo method. The diffusion coefficients obtained will be compared with the experimental data obtained from experimental collaborators. NiAl will thus become the first ordered system, probably even the first binary system, where diffusion of both species in the lattice and along the grain boundaries will be studied by both experimental and theoretical methods. %%% This project is aimed at theoretical investigations and computer simulations of point defects and grain boundaries, as well as diffusion in the lattice and along grain boundaries in ordered compounds. The focus of research will be the intermetallic compound NiAl. The project includes collaborations with groups working on ab initio calculations and on diffusion experiments. NiAl will thus become the first ordered system, probably even the first binary system, where diffusion of both species in the lattice and along the grain boundaries will be studied by both experimental and theoretical methods. ***

这个项目的目的是理论研究和计算机模拟点缺陷和晶界，以及在有序化合物中的晶格和沿晶界的扩散。研究的重点是金属间化合物NiAl。该项目包括与从事从头计算和扩散实验的小组合作。金属间化合物的原子结构和沿晶界的扩散与它们有限的延展性和高温蠕变性能有关。NiAl的晶界扩散从未在实验或理论上进行过研究。此外，由于跳跃相关理论的提出和相应模拟方法的发展，正确的晶界扩散系数的原子计算最近才成为可能。这些理论和模拟技术将进一步完善并应用于NiAl的晶界研究。通过拟合实验性质和从头计算结果，将开发出与角相关的嵌入原子型半经验势。利用分子静力学和动力学方法计算001和011对称倾斜晶界的原子结构。计算了点状缺陷在晶格和晶界的形成能和平衡浓度。计算了原子在晶格和晶界核中不同机制下的迁移能。得到的点缺陷浓度和迁移能将利用跳变相关理论和蒙特卡罗方法计算Ni和Al的晶格和晶界扩散系数。得到的扩散系数将与实验合作者得到的实验数据进行比较。因此，NiAl将成为第一个有序系统，甚至可能是第一个二元系统，在这个系统中，两种物质在晶格中的扩散和沿晶界的扩散将通过实验和理论方法来研究。这个项目的目的是理论研究和计算机模拟点缺陷和晶界，以及在有序化合物的晶格和沿晶界扩散。研究的重点是金属间化合物NiAl。该项目包括与从事从头计算和扩散实验的小组合作。因此，NiAl将成为第一个有序系统，甚至可能是第一个二元系统，在这个系统中，两种物质在晶格中的扩散和沿晶界的扩散将通过实验和理论方法来研究。＊＊＊