石墨烯/炔纳米材料衬底上分子齿轮联动机制及调控研究

Two-dimensional(2D) Dirac nanomaterials such as graphene and graphyne have become a hot material in the field of molecular electronics, because they have a variety of C-C bonds and perfect chemical stability. By using ab initio calculations based on the density functional theory combined with nonequilibrium Green’s function formalism, the "sandwich-like" stable model of molecular gear will be constructed on the graphene or graphyne substrates with the ferrocene stable structure, and the molecular dynamics model could be established by molecular dynamics simulation. Certainly, we can manipulate the rotation angle of driving wheel and the layer spacing among molecular gear, heavy metal rotating shaft and nanoribbon in order to achieve the mechanism of stable linkage on the driven wheel on the 2D nanomaterial surface by employing the principle of minimum energy. Further, the stable rotational model of the molecular gears on the substrate of Dirac materials are expected to be displayed, and the spin transport properties induced by the rotation of molecular gears are regulated by means of the ferromagnetic doping, the atom replacement of rotating axis, the edge modification of ribbon and the electromagnetic field, etc. In this project, the intrinsic mechanism of the device effect could be deeply analyzed by means of the projected density of state , the local density of state, the evolution of the frontier molecular orbital and so on. The purpose of this project is to provide a theoretical direction for the experimental study of the molecular gears on the substrate of graphene and graphyne. It maybe promote the development of molecular devices from the basic research to the practical diversification.

石墨烯/炔等二维Dirac纳米材料具有种类丰富的碳-碳化学键、良好的化学稳定性等优异物理化学性质，成为分子电子学研究领域的热门材料。本项目拟采用密度泛函理论与非平衡格林函数相结合的第一性原理方法，在石墨烯/炔等碳基纳米材料衬底上利用二茂铁稳定结构构建出“三明治”状分子齿轮的稳定模型，并对体系开展分子动力学模拟确定分子动力学仿真模型；通过操纵分子齿轮、重金属转动轴与纳米带的层间距及其驱动轮的转动角度等因素，利用能量最低原理确定从动轮的稳定联动机制，揭示联动分子齿轮在二维材料表面的稳定运转机制；采取铁磁掺杂、转动轴原子置换、条带边缘修饰、外加电磁场等多种手段对分子齿轮转动诱导的自旋输运性质进行调控，利用投影态密度、局域态密度、体系前线轨道分布等分析方法深入剖析相关器件效应产生的内在内在机理。旨在为后续分子齿轮在二维材料表面的实验研究提供理论依据，促进分子器件由基础研究向实践多元化发展。

分子齿轮作为分子马达、分子器件制备的基础元件，已成为物理、化学、材料等学科交叉领域研究的热点。本项目根据有效原子序数法则(EAN)，旨在将有机分子齿轮镶嵌在石墨烯/炔衬底表面构建马达模型，研究多分子齿轮的联动机理，开展光电场、掺杂、边缘修饰、应变、自旋、及电磁场调控对石墨烯/炔纳米条带热电输运性质的影响。3年来，本项目组通过与国内外理论、实验团队合作研究，基本完成研究任务计划，达到预期研究目标。项目执行期间取得的成果概述如下：利用密度泛函理论与非平衡格林函数相结合的方法，我们利用二茂铬稳定结构构建C_6分子齿轮层状模型，设计出分子齿轮在二维材料衬底上转动轴模型；进一步考虑外加电磁场对纳米带电子能带结构、热电输运性质的调控及分子齿轮转动机制的影响。研究发现在一定电场强度范围内，外加电场有利于减小齿轮联动的转动势垒；电场作用能够诱发联动齿轮与纳米带组合体系的双致开关效应。我们预测了α-2-石墨炔、γ-石墨炔、δ-石墨炔、碳磷条带等二维纳米条带的良好结构稳定性，因其具有自旋过滤、自旋塞贝克效应等输运性质可用于开发自旋热电器件。研究发现，锯齿型δ-石墨炔纳米带在反自旋铁磁注入时展现出自旋过滤、整流效应，其整流比达到10^6%；碳磷条带分子结的自旋极化系数高达99%，NDR效应峰谷比达到10^5。此外，对螺旋桨齿轮等复杂体系齿轮转动模式开展深入研究，设计出有利于减小马达分子转动势垒的多层齿轮转动轴模型，发现γ-石墨炔、δ-石墨炔等条带适合于构建AIE螺旋桨齿轮的联动模型衬底。进一步考虑声子散射对分子结的热电输运影响，预测了一些新奇的物理化学现象。本项目选择石墨烯/炔条带作为分子齿轮的组装基底，在分子马达研究领域具有前沿创新意义。我们将柔性材料衬底引入分子器件、分子汽车继续开展深入研究，寻求器件输运特性的内在调控机制，将为分子电子学领域实验探索提供理论基础。