Solid State Oxyfluorides

该项目的重点是基于非中心过渡金属氟氧化物的非中心对称结构中分子组分的化学性质的晶体结构的合理设计。用于从金属氧化物制备金属氟氧化物的稳健合成方法允许同时进行许多反应，这大大提高了反应产率、受控纯度和单晶生长。偏心分子和固体是那些缺乏反转对称性的分子和固体。 一个主要的目标是了解如何优化几何形状和静电势的个别氟氧化物阴离子，以创建秩序，避免无序的金属-氧和金属-氟键。 氟氧化物的晶体对称性由周围晶格提供的接触网络决定，控制接触网络以产生手性、极性或手性-极性三维固体。 缺乏反转对称性的结构是重要的当前和未来技术的要求，这些技术是由基于压电性、热电性、铁电性和二次谐波产生（SHG）的众多发明创造的。 其目的是为基础科学中与非中心对称空间群相关的研究提供一类新的固体。 加强研究和教育的基础设施是一个关键目标。与西北大学的材料研究科学与工程中心（MRSEC）和催化与表面科学中心（CCSS）保持着密切的联系。 这些中心鼓励、支持和运营多用户设施，并为学生提供培训，以促进高水平的科学成就和专业发展。 本科生，研究生和研究生学生受益于新材料的发现以及从这些新结构及其特性的表征中获得的跨学科经验所取得的重大进展。 学生有一切机会在科学会议上发表演讲，在那里他们可以与工业和学术同事互动。 结构/性能关系的确定正在进行，包括基本结构研究（X射线、中子和电子衍射和显微镜）、热动力学性能（热重分析和差示扫描量热法）以及光学和磁性性能（IR、拉曼和SQUID）。 与国家实验室，特别是与阿贡国家实验室，特别是与橡树岭国家实验室正在开发的强脉冲中子源和新的散斑中子源的科学家保持密切联系。 展示压电性，热电性，铁电性和二次谐波产生（SHG）的新材料课程具有重要意义，因为应用材料和在这些及相关领域接受培训的学生在就业市场上非常有竞争力。

The focus of this project is on the rational design of crystal structures based on the chemical nature of molecular components in noncentrosymmetric structures based on acentric transition metal oxyfluorides. Robust synthetic methods used to prepare metal oxyfluorides from metal oxides allow many reactions to be carried out simultaneously, which greatly enhances reaction yields, controlled purity, and single crystal growth. Acentric molecules and solids are those that lack inversion symmetry. A major goal is to understand how to optimize geometries and the electrostatic potential of the individual oxyfluoride anions to create order and avoid disorder in the metal-oxygen and metal-fluoride bonds. Crystal symmetries of the oxyfluorides are determined by the network of contacts the surrounding lattice provides which are controlled to create chiral, polar or chiral-polar three-dimensional solids. Structures lacking inversion symmetry are a requirement for important current and future technologies that are being created by numerous inventions based on piezoelectricity, pyroelectricity, ferroelectricity and second harmonic generation (SHG). The goal is to provide is to provide a new class of solids for studies in basic science associated with the noncentrosymmetric space groups. %%%Enhancing the infrastructure of research and education is a key objective. Strong ties are maintained with the Materials Research Science and Engineering Center (MRSEC) and the Center for Catalysis and Surface Science (CCSS) at Northwestern University. These centers encourage, support and operate multi-user facilities and provide training for the students which facilitate a high level of scientific achievement and professional development. Undergraduate, graduate and post-graduate students benefit from the significant advances that can be made in the discovery of new materials and from the cross-disciplinary experiences gained from the characterization of these new structures and their properties. Students are given every opportunity to give presentations at scientific meetings where they can interact with industrial and academic colleagues. The determination of structure/property relationships is ongoing with basic structural studies (X-ray, neutron and electron diffraction and microscopy), thermo-dynamic properties (thermogravimetric analysis and differential scanning calorimetry), and optical and magnetic properties (IR, Raman and SQUID). Strong ties are also maintained with National Laboratories especially Argonne National Laboratory, and in particular with scientists at the Intense Pulsed Neutron Source (IPNS) and the new Spallation Neutron Source (SNS) under development at Oak Ridge National Laboratory. New materials classes exhibiting piezoelectricity, pyroelectricity, ferroelectricity and second harmonic generation (SHG) are of significant interest as applied materials and students trained in these and related areas are very competitive in the job market.***