Carbon Nanostructures: Surface-Mediated Mechanical Response and Topologically Constrained Bonding

该奖项支持纳米材料研究领域的计算和理论研究和教育。通过计算机模拟，该项目开发了几种新的材料和基于材料的系统，可用于纳米级应用。一种正在开发的材料是由阳离子和阴离子的单层包围石墨片组成的二维铁电片。系统的调查作为单和双金属阳离子的功能，由卤素，硫属化物和多原子阴离子补偿正在进行中。 研究的第二个领域涉及由碳纳米结构组成的纳米机械致动器的发展。根据环境的不同，这些结构可能会弯曲或倒塌。在衬底上构造这种致动器将提供密集的压力依赖性机械存储器件、气体传感器和杠杆。特别强调的是确定临界长宽比，尺寸和屈曲角，在该系统可以恢复，有或没有滞后，以及那些导致不可逆的改变的条件。 第三个相关的调查领域涉及同心同轴碳纳米管的发展，以调查开发纳米级活塞，螺杆和传感器的可能性。最后的努力涉及从N2O和NO2分子构建的开放扩展框架的发展。重点是确定产生稳定相所需的压力，并确定它们在较低压力下是否是亚稳的。 所有这些问题的共同点是需要和使用精确的密度泛函方法、经验势和紧束缚方法来确定电子和振动效应。 PI将通过一项针对高中适龄学生的基于互联网的科学推广活动来传播他的研究成果。非技术总结：该奖项支持计算和理论研究和教育，使用复杂的计算建模技术来确定新的纳米系统将以有用的功能运行的环境条件。 一个焦点是确定导致刚性轻质碳基纤维弯曲和屈曲的条件。这种纤维可用于构建机械存储装置和传感器。 当这些纤维被布置为纳米级同轴电缆时，其具有与小型化活塞、螺钉和换能器相关的进一步应用。这里的研究集中在这些纤维的直接应用，以及它们用于操纵和能量转移到原子和分子。 基于这里研究的一些碳基材料和纳米系统，正在进行更多的计算机模拟，研究由氮和氧组成的类似结构的制造。 此外，还在模拟一种轻质、坚固的碳基薄膜，该薄膜的一面涂有金属箔，另一面涂有类似特氟隆的片材。PI将通过一项针对高中适龄学生的基于互联网的科学推广活动来传播他的研究成果。

TECHNICAL SUMMARY:This award supports computational and theoretical ressearch and education in the area of materials research at the nanoscale. Through computer simulation, this project develops several new classes of materials and materials-based systems amenable to use for nanoscale applications. One material under development is a two-dimensional ferroelectric sheet composed of monolayers of cations and anions sandwiching a graphite sheet. Systematic investigations as a function of single and double metallic cations compensated by halogens, chalcogenides and polyatomic anions are underway. A second area of investigation deals with the development of nanomechanical actuators composed of bistable carbon structures. Depending upon the environment these structures may either buckle or collapse. Construction of such actuators on substrates will provide for dense pressure-dependent mechanical memory devices, gas sensors and cantilevers. Particular emphasis is on determining critical aspect ratios, sizes and buckling angles at which the system can recover, with or without hysteresis, and those conditions which lead to irreversible alteration. A third related area of investigation deals with the development of concentric coaxial carbon nanotubes to investigate the possibility of developing nanoscale pistons, screws and transducers. The final effort deals with the development of open extended frameworks built from N2O and NO2 molecules. Emphasis is on determining pressures required to create stable phases and determine if they are metastable at lower pressures. These projects are performed in concert with substantial experimental collaboration.Common to all of these problems is the need for and use of accurate density functional methods, empirical potentials and tight-binding methodologies to determined both electronic and vibrational effects. The PI will spread the excitement of his research through an internet-based scientific outreach effort aimed at high-school-age students. NON-TECHNICAL SUMMARY:This award supports computational and theoretical ressearch and education that uses sophisticated computational modeling techniques to determine the environmental conditions at which novel nanoscale systems will operate with useful function. One focus is to determine the conditions that cause stiff lightweight carbon-based fibers to bend and buckle. Such fibers may be used to build mechanical memory devices and sensors. These fibers when arranged as a nanoscale coaxial cable have further applications related to miniaturized pistons, screws and transducers. Research here concentrates on immediate application of such fibers and on their use for manipulation of and energy transfer to atoms and molecules. Based upon some of the carbon-based materials and nanosystems studied here, additional computer simulations which investigate fabrication of similar structures composed of nitrogen and oxygen are underway. Simulation of a lightweight strong carbon-based film coated with a metallic foil on one side and a Teflon-like sheet on the other is also underway. The PI will spread the excitement of his research through an internet-based scientific outreach effort aimed at high-school-age students.