Point Defects in Intermetallics using PAC

用伽马射线的摄动角相关（PAC）研究了金属间化合物中的collinpoint缺陷。通过测量特征四极相互作用，确定了稀铟探针原子的局部环境。研究了两种环境：探针原子作为溶质在化合物或相的混合物中作为不相等晶格位的溶质；探针结合在晶格空位的配合物中。研究的三个领域是最近工作的自然延伸。溶质原子对化合物或两相合金中不同点阵位置的偏好是通过测量探针原子在不同点阵位置的分数来确定的。通过将测量的四极相互作用与具有相同结构的一系列化合物中的四极相互作用进行比较并计算四极相互作用来确定亚晶格位点。目标是对网站偏好有更系统的了解。在室温下，利用金刚石砧细胞研究了外加压力对结合在晶格空位配合物中的探针的四极相互作用的影响。期望在空位配合物附近会有较大的原子弛豫。压力依赖性将与温度依赖性以及配合物的结构和电场梯度的计算相关联。目的是了解空位团簇的形状和体积在压力和温度的影响下是如何变化的。涉及点缺陷的四个过程将被研究：缺陷的形成、空位与探针原子的结合、非化学计量化合物中不同结构点缺陷之间的转换以及空位迁移。前三个过程的激活体积将通过测量探针空位复合物的位点分数来确定。空位迁移的激活体积将由探针原子附近空位随机跃迁引起的信号松弛的压力依赖性来确定。这些测量将提供关于点缺陷过程的基本信息。这将是第一次使用金刚石砧细胞进行高压PAC研究，也是第一次在高温下进行高压PAC研究。这一领域的研究结果对于使用PAC和类似方法研究日益复杂的系统的研究人员应该是有用的

0091681 CollinsPoint defects in intermetallic compounds are studied using perturbed angular correlation of gamma rays (PAC). Local environments of dilute indium probe atoms are resolved through measurement of characteristic quadrupole interactions. Two kinds of environment are studied: probe atoms as solutes on inequivalent lattice sites in a compound or mixture of phases, and probes bound in complexes with lattice vacancies. Research is in three areas that are natural extensions of recent work. Preferences of solute atoms for different lattice sites in compounds or in two-phase alloys are determined through measurement of fractions of probe atoms in the different sites. Sublattice sites are identified by comparing measured quadrupole interactions with those in a series of compounds having the same structure and with computations of quadrupole interactions. The goal is to develop a more systematic understanding of site preferences. The effect of applied pressure on the quadrupole interactions of probes bound in complexes with lattice vacancies are studied at room temperature using a diamond anvil cell. The expectation is that there will be large relaxations of atoms near vacancy complexes. Pressure dependencies will be correlated with temperature dependencies and with computations of the structures and electric-field gradients of the complexes. The goal is to understand how the shape and volume of vacancy clusters change under the influence of pressure and temperature. Four processes involving point defects will be studied: defect formation, binding of vacancies to probe atoms, conversion between different structural point defects in non-stoichiometric compounds, and vacancy migration. Activation volumes for the first three processes will be determined through measurement of site fractions of probe-vacancy complexes. The activation volume for vacancy migration will be determined from the pressure dependence of signal relaxation caused by stochastic jumping of vacancies near probe atoms. %%%These measurements will provide fundamental information about point defect processes. These will be the first high pressure PAC studies carried out using a diamond anvil cell and the first at high temperature. Results in this area should be useful to researchers studying increasingly complex systems using PAC and similar methods.***