Solid State Oxyfluorides

技术概述需要在微观和宏观水平上具有增强的光学性能的高性能非线性光学(NLO)材料的技术依赖于表现出大的光学非线性(具有偶极)的无机材料。合理设计晶体结构，特别是非中心对称材料，以及如何区分极性、极性-手性和手性结构，是晶体工程中正在进行的主题。这些材料对于修改光信号的幅度、相位或频率是必不可少的。金属中心八面体中的极性失真是金属氧化物非线性光学响应的根源。4、5、6族八面体配位过渡金属阳离子在混合金属氧化物中的八面体内扭曲是不稳定的，这可以用二阶Jahn-Teller定理来解释。本程序探索了基于偏心过渡金属氧氟化物的非中心对称结构的研究。这些材料将提供一大类新的固体，具有与压电性、热释电性、铁电性和二次谐波产生(SHG)相关的性质，所有这些性质都与非中心对称空间群有关。这项工作得到了材料研究部固体和材料化学计划的资助。非技术概述基于分子组成的化学性质进行结构的合理设计是有机固态化学中一个长期而令人兴奋的研究课题，是晶体工程的一个新兴主题。然而，需要具有增强光学性能的高性能非线性光学(NLO)材料的技术依赖于表现出大光学非线性的无机材料。缺乏反转对称性的结构是重要的当前和未来技术的要求，这些技术是过去二十年中由许多发明创造的。这些材料为与非中心对称空间群相关的基础科学研究提供了一大类新的固体。我们提出了一个关于这些材料的探索性研究计划，最近在一篇题为《中国的水晶缓存》的文章中强调了这一点。在《自然》杂志的这篇文章中，强调了国家迫切需要以合成为基础的努力，以发现和生长这些新材料的合适晶体。这项工作得到了国家科学基金会材料研究部固体和材料化学计划(DMR-1005827)的资助。

Technical SummaryTechnologies that require high-performance nonlinear optical (NLO) materials with enhanced optical properties at the microscopic and macroscopic level depend on inorganic materials that exhibit large optical nonlinearities (possessing a dipole). The rational design of crystal structures, in particular noncentrosymmetric materials, and how to differentiate polar, polar-chiral, and chiral structures, is an ongoing theme in crystal engineering. These materials are essential for the modification of the amplitude, phase, or frequency of an optical signal. Polar distortions in metal centered octahedra are the origin of the nonlinear optical response in metal oxides. Octahedrally coordinated transition metal cations in groups 4,5,6 are unstable in mixed metal oxides with respect to intraoctahedral distortions, which can be understood through the second order Jahn-Teller theorem. This program explores research on noncentrosymmetric structures based on acentric transition metal oxyfluorides. These materials will provide a large and new class of solids with properties associated with piezoelectricity, pyroelectricity, ferroelectricity and second harmonic generation (SHG), all properties associated with noncentrosymmetric space groups. This work is supported by a grant from the Solid State and Materials Chemistry Program in the Division of Materials Research.Non-technical SummaryThe rational design of structures based on the chemical nature of molecular components, a longstanding and exciting research topic in organic solid-state chemistry, is an emerging theme of crystal engineering. Technologies that require high-performance nonlinear optical (NLO) materials with enhanced optical properties, however, depend on inorganic materials that exhibit large optical nonlinearities. Structures lacking inversion symmetry are a requirement for important current and future technologies that have been created by numerous inventions during the past two decades. These materials provide a large and new class of solids for studies in basic science associated with the noncentrosymmetric space groups. We propose an exploratory research program on these materials, which were highlighted recently in an article entitled "China's Crystal Cache" (Nature 2009, 457, 953-955). In this Nature article the critical national need for synthesis-based efforts to discover and to grow suitable crystals of these new materials was emphasized. This work is supported by a grant from the Solid State and Materials Chemistry Program in the Division of Materials Research at the National Science Foundation (DMR-1005827).