Atomistic Theory and Computer Simulation of Grain Boundary Structure and Diffusion

9753243 Farkas这个项目的目的是点缺陷和晶界的理论研究和计算机模拟，以及在晶格中的扩散和有序化合物中的沿着晶界。 研究的重点将是金属间化合物NiAl。 该项目包括与从事从头计算和扩散实验的小组合作。 金属间化合物中的原子结构和沿沿着的扩散与其有限的延展性和高温蠕变抗性有关，因此受到极大关注。 NiAl中的晶界扩散从来没有实验或理论研究。 此外，正确的晶界扩散系数的原子计算最近才成为可能，由于工作所做的建议者的跳跃相关理论和各自的模拟方法的发展。 这些理论和模拟技术将进一步完善和应用于NiAl晶界。 通过拟合实验性质和从头计算结果，得到了NiAl的嵌入原子型角依赖半经验势。 001和011的原子结构 将使用分子静力学和动力学计算对称倾斜晶界。 将计算晶格和晶界中点缺陷的形成能和平衡浓度。 还将计算晶格和晶界核中不同机制的原子迁移能。 点缺陷浓度和迁移能量将用于计算的晶格和晶界扩散系数的Ni和Al使用跳跃相关理论和Monte Carlo方法的新方法。 将获得的扩散系数与实验合作者获得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，其中两种物质在晶格中和沿着晶界的扩散将通过实验和理论方法进行研究。 该项目的目的是对有序化合物中的点缺陷和晶界，以及晶格中的扩散和沿着晶界的扩散进行理论研究和计算机模拟。 研究的重点将是金属间化合物NiAl。 该项目包括与从事从头计算和扩散实验的小组合作。 NiAl因此将成为第一个有序系统，甚至可能是第一个二元系统，其中两种物质在晶格中和沿着晶界的扩散将通过实验和理论方法进行研究。 ***

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. ***