Bulk and Interface Bonding in Ceramics and Intermetallics

斯宾塞9412146提出了一项关于晶体中、界面和缺陷处的原子成键的三年研究计划。陶瓷和金属间化合物的研究将结合从头计算、自洽计算和定量会聚束电子衍射法的键电荷分布的实验测量。亚利桑那州立大学高分辨率电子显微镜中心的蔡司欧米茄能量过滤电子显微镜将用于实验工作。主要投资者提出了一种新技术，该技术基于金属-陶瓷界面在传输几何中反射的镜面电子束，用于反射成像、微观分析和埋藏界面的结合研究。这项工作是与C.P.弗林合作的。对于最近才首次看到键的完美晶体，主要投资者建议测量钛铝和一系列离子晶体中的键电荷分布，以测试基于局部密度近似的自洽计算的准确性。测量的键分布将比较钛-铝掺杂和不掺杂锰的情况，发现锰掺杂可以降低脆性。在铁电晶体中，主要研究人员计划比较钛酸锶和同构钛酸钡中钛和氧之间的电荷转移，以了解为什么一个是铁电的，另一个不是。%这项拟议的研究旨在调查晶体中原子成键的起源，包括界面和缺陷。陶瓷和金属间化合物将使用理论计算和定量技术的键电荷分布实验测量相结合的方法进行研究。***

Spence 9412146 A three year program of research is proposed of atomic bonding in crystals, at interfaces and at defects. Ceramics and intermetallic compounds will be studied using a combination of ab-initio quantum molecular dynamics computations, self-consistent calculations and experimental measurements of bond charge distributions by quantitative convergent beam electron diffraction method. The Zeiss Omega energy-filtering electron microscope at the Arizona State University center for High Resolution Electron Microscopy will be used for the experimental work. Principal Investors propose a new technique based on the specular electron beam reflected from a metal-ceramic interface in the transmission geometry for reflection imaging, microanalysis and bonding studies of buried interfaces. This work is collaborative with C.P. Flynn. For perfect crystals, in which bonds have been "seen" for the first time only recently, Principal Investors propose bond charge distribution measurements in titanium-aluminum and a series of ionic crystals in order to test the accuracy of self-consistent computations based on the local density approximation. Measured bond distributions will be compared for titanium-aluminum with and without manganese doping, which is found to reduce brittleness. In ferroectric crystal Principal Investigators plan comparisons of charge transfer between titanium and oxygen in strontium titanate and isostructural barium titanate oxygen in order to understand why one is ferroelectric and the other not. %%% The proposed research seeks to investigate the origins of atomic bonding in crystals, at interfaces and defects. Ceramics and intermetallic compounds will be studied using a combination of theoretical calculations and experimental measurements of bond charge distributions by quantitative techniques. ***