Squeezing Simple Molecules to Novel Conducting Polymers

技术概述：在足够高的压力下，所有分子都有望转变为金属延伸固体，可以被认为是元素金属或金属合金。由H、C、N和O等低Z元素组成，这些延伸的固体构成了一类新的高导电性有机聚合物或分子合金，可以表现出金属导电性和新的电子和化学性质。我们提出了一个系统的研究压力诱导的高共价族IV、V和VI元素分子（如C、N2、CO2）及其化学类似物向(a)金属和超导态、(B)电荷/自旋有序态和(C)低维金属态的新型扩展固体的转变。在Mbar压力下（1mbar ~ 100gpa = 106个大气压），该研究将使用集成的实验能力来探测晶体结构（同步x射线衍射）、电子结构（非弹性x射线拉曼光谱和光学反射率）、电传输特性（四探针电阻和磁化率）以及相变和键合（拉曼和红外光谱）。由固态和材料化学计划支持的拟议研究将在元素合金的最基本水平上建立低Z分子固体的新周期视角。在此过程中，我们将探索在极端条件下扩展固体的几个关键科学挑战：(i)结构有序（或无序）与电子结构之间的关系，（ii）分子绝缘体到金属转变附近的电荷和自旋有序过程，（iii）低维和/或不相称结构中的内部压力的性质，以及（iv）低Z共价聚合物和高Z金属合金之间的差异（或相似之处）。解决这些挑战不仅对理解晶体结构、电子相关性和功能特性的关系很重要，而且对环境条件下新材料和技术的发展也有很大的影响。非技术总结：目前的研究将影响广泛的科学学科，包括凝聚态物理、固态化学、材料和行星科学。它将产生新的和意想不到的发现，并有助于在极端压力下建立新的低Z元素固体的周期系统。这项研究还将利用化学合金和内部压力的概念，帮助开发一种在环境条件下的新型高导电性金属和超导聚合物。这项研究将扩大和加强与国家实验室、同步加速器x射线设施和其他学术机构的合作。因此，其好处将远远超出本建议的直接范围。我们将培养研究生、本科生和博士后，为学习前沿实验技术提供重要的实践机会。目前的工作将为他们提供职业发展和开展独立研究所需的关键工具。最后，该研究将产生各种实时图像和电影，展示晶体切面和元素固体的美丽，揭示大自然迷人的结构和形态变化。这将有许多用途，其中包括激发K-12和本科生对这一基础物理科学研究的科学想象力和兴奋。

TECHNICAL SUMMARY: At sufficiently high pressures, all molecules are expected to transform into metallic extended solids that can, arguably, be considered either elemental metals or metallic alloys. Made of low Z elements such as H, C, N, and O, these extended solids constitute a new class of highly conductive organic polymers or molecular alloys that can exhibit metallic conductivities and novel electronic and chemical properties. We propose a systematic study of pressure-induced transformations of highly covalent Group IV, V, and VI elemental molecules such as C, N2, CO2, and their chemical analogs to novel extended solids of (A) metallic and superconducting states, (B) charge/spin-ordered states, and (C) low-dimensional metallic states. The proposed study will use integrated experimental capabilities to probe crystalline structures (synchrotron x-ray diffraction), electronic structures (inelastic x-ray Raman spectroscopy and optical reflectivity), electrical transport properties (four-probe resistance and susceptibility), as well as phase transitions and bonding (Raman and IR spectroscopy), at Mbar pressures (1 Mbar ~ 100 GPa = 106 atmospheres). The proposed research, supported by the Solid State and Materials Chemistry Program will establish a new periodic perspective on low Z molecular solids at the most fundamental level of elemental alloys. In doing so we will explore several key scientific challenges of extended solids under extreme conditions: (i) the relationships between structural orders (or disorders) and electronic structures, (ii) the charge and spin ordering processes near molecular insulator-to-metal transitions, (iii) the nature of internal pressures in low-dimensional and/or incommensurate structures, and (iv) the differences (or similarities) between low Z covalent polymers and high Z metallic alloys. Addressing these challenges is not only important in understanding the relationships of crystalline structures, electron correlation, and functional properties, but will also have strong implications for novel materials and technology developments at ambient conditions.NON TECHNICAL SUMMARY: The present study will impact broad scientific disciplines including condensed matter physics, solid-state chemistry, and materials and planetary sciences. It will yield new and unexpected discoveries and help establish new periodic systematics of low Z elemental solids at extreme pressures. The study will also help develop a new class of highly conducting metallic and superconducting polymers at ambient conditions, utilizing the concept of chemical alloys and internal pressures. The study will augment and enhance collaborations with national laboratories, synchrotron x-ray facilities, and other academic institutes. Hence, the benefits will reach well beyond the immediate scope of the present proposal. We will train graduate students, undergraduates and post-doctoral fellows, providing significant hands-on opportunities to learn cutting-edge experimental technologies. The present work will provide them with critical tools needed for career development and carrying out independent research. Finally, the proposed study will produce a variety of real-time images and movies showing the beauty of crystal facets and elemental solids and revealing nature's fascinating structural and morphological transformations. These will have many uses, among them, stimulating the scientific imagination and excitement of both K-12 and undergraduate students in this fundamental physical science research.