NSF/DMR-BSF: Growth Induced Crystal Curvature

伟大的晶体学家舒布尼科夫说："晶体闪现出它们的对称性。"他在这句精辟的话中强调了晶体的特征，它们引人注目的多面体形状，有锋利的边缘和平坦的表面;晶体，根据定义，是直的。见证多面宝石，或自然生长的石英。然而，人们在大约世纪前就认识到，可以使各种各样的晶体以扭曲的、螺旋状的形态生长--这些形态显然不是直的。值得注意的是，水晶王国的这一普遍特征在很大程度上被遗忘了，尽管它是阿司匹林等常见物质的特征。在固态和材料化学项目的支持下，研究小组的目标是了解晶体在生长时如何扭曲。这些过程是了解由分子构建的晶体的机械性能的窗口，这些过程是重要工业操作（如药物压片）的基础。扭曲的晶体在它们有节奏的光学对比带中是生动的，有望成为微观和宏观手形之间的桥梁。该研究团队与几所布朗克斯公立高中合作，以提供科学身份建设研究经验。技术文摘生长引起的形状变形的起源大概在于混合晶体的超分子化学和这些力在固体的机械性质中表现出来的方式。 该团队已经表明，添加剂在生长的晶体界面处诱导立体特异性扭曲。添加剂可能通过产生具有不同度量性质的混合畴来扭曲晶体。在分子水平上的不匹配产生应变，而应变又可以产生应力和扭转力矩。该战略有三个方面：1。建立了取代苯的混合或无序晶体的扭曲条件，我们已经从长期的单晶研究中了解了生长诱导应变的起源。2.利用先进的显微镜技术精确地描述具有生长诱导曲率的晶体的形状--这项工作正在与E。Efrati在魏茨曼科学研究所的合作安排下，由材料研究部和美国-以色列两国科学基金会建立。3.魏茨曼的扭曲带微分几何专家正在分析增长变形的几何挫折编码的局部差异增长的框架内。这些研究将与原子力场和分子动力学模拟相匹配。

Non-Technical AbstractThe great crystallographer Shubnikov said that "crystals flash forth their symmetry." He was emphasizing in this pithy remark the characteristic feature of crystals, their striking polyhedral shapes with sharp edges and flat faces; crystals, by definition, are straight. Witness facetted gemstones, or naturally grown quartz. However, it was recognized almost a century ago that a wide variety of crystals can be made to grow with twisted, helix-like morphologies -- forms that are decidedly not straight. Remarkably, this general feature of the crystal kingdom was largely forgotten, even though it is characteristic of common substances such as aspirin. With support from the Solid State and Materials Chemistry program, the research team aims to understand how crystals twist themselves as they grow. These processes are windows into the mechanical properties of crystals built from molecules, processes that underlie important industrial operations such as the tableting of pharmaceuticals. Twisted crystals are vivid in their rhythmic bands of optical contrast, promising a bridge between microscopic and macroscopic handed forms. The research team is partnered with several Bronx public high schools in order to provide science identity-building research experiences. Technical AbstractThe origin of growth induced deformations of form presumably lie in the supramolecular chemistry of mixed crystals and in the manner in which these forces are manifest in the mechanical properties of solid bodies. The team has shown that additives induce twisting stereospecifically at growing crystal interfaces. Additives likely twist crystals by creating mixed domains with distinct metric properies. Mismatches at the molecular level produce strain that in turn can generate stress and twist moments. The strategy is threefold: 1. Establishing the conditions for twisting mixed or disordered crystals of substituted benzenes about which we already understand the origin of growth induced strain from long-standing studies of single crystals. 2. Using advanced microscopies to accurately describe the shapes of crystals with growth induced curvature -- this work is proceeding in collaboration with Professor E. Efrati at the Weizmann Institute of Science under the collaborative arrangement established by the Division of Materials Research and the US-Israel Binational Science Foundation. 3. Weizmann experts in differential geometry of twisted ribbons are analyzing growth deformation within the framework of geometric frustration encoded in local differential growth. These studies will be matched with atomistic force-field and molecular dynamics simulations.