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首页> 外文学位 >Theoretical descriptions of electron transport through single molecules: Developing design tools for molecular electronic devices.
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Theoretical descriptions of electron transport through single molecules: Developing design tools for molecular electronic devices.

机译：电子通过单分子传输的理论描述：开发用于分子电子设备的设计工具。

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There are vast numbers of organic compounds that could be considered for use in molecular electronics. Hence there is a need for efficient and economical screening tools. Here we develop theoretical methods to describe electron transport through individual molecules, the ultimate goal of which is to establish design tools for molecular electronic devices. To successfully screen a compound for its use as a device component requires a proper representation of the quantum mechanics of electron transmission. In this work we report the development of tools for the description of electron transmission that are: Charge self-consistent, valid in the presence of a finite applied potential field and (in some cases) explicitly time-dependent. In addition, the tools can be extended to any molecular system, including biosystems, because they are free of restrictive parameterizations. Two approaches are explored: (1) correlation of substituent parameter values (sigma), (commonly found in organic chemistry textbooks) to properties associated with electron transport, (2) explicit tracking of the time evolution of the wave function of a nonstationary electron. In (1) we demonstrate that the a correlate strongly with features of the charge migration process, establishing them as useful indicators of electronic properties. In (2) we employ a time-dependent description of electron transport through molecular junctions. To date, the great majority of theoretical treatments of electron transport in molecular junctions have been of the time-independent variety. Time dependence, however, is critical to such properties as switching speeds in binary computer components and alternating current conductance, so we explored methods based on time-dependent quantum mechanics. A molecular junction is modeled as a single molecule sandwiched between two clusters of close-packed metal atoms or other donor and acceptor groups. The time dependence of electron transport is investigated by initially localizing an electron on the donor and following the time development of the corresponding non-stationary wavefunction of the time-independent Hamiltonian. We demonstrate that the time-dependent treatment of electron transport predicts physically intuitive results, while providing insights not available from time-independent methods.
机译：可以考虑将大量有机化合物用于分子电子学。因此，需要有效且经济的筛选工具。在这里，我们开发了描述电子通过单个分子传输的理论方法，其最终目的是为分子电子设备建立设计工具。为了成功地筛选出用作设备组件的化合物，需要正确表示电子传输的量子力学。在这项工作中，我们报告了用于描述电子传输的工具的开发，这些工具是：电荷自洽，在有限的施加电势场下有效，并且（在某些情况下）明确地依赖时间。另外，这些工具可以扩展到任何分子系统，包括生物系统，因为它们没有限制性的参数设置。探讨了两种方法：（1）取代基参数值（sigma）（通常在有机化学教科书中找到）与与电子传输相关的特性的相关性；（2）显式跟踪非平稳电子的波函数的时间演化。在（1）中，我们证明了a与电荷迁移过程的特征密切相关，并将其确立为电子性质的有用指标。在（2）中，我们采用时间依赖的方式描述电子通过分子结的传输。迄今为止，分子结中电子传输的绝大多数理论方法都是与时间无关的。但是，时间依赖性对于诸如二进制计算机组件中的开关速度和交流电导率之类的属性至关重要，因此我们探索了基于时间依赖性量子力学的方法。分子连接被建模为夹在两个紧密堆积的金属原子或其他供体和受体基团之间的单个分子。通过首先将电子定位在施主上，并跟随与时间无关的哈密顿量的相应非平稳波函数的时间发展，来研究电子传输的时间依赖性。我们证明了电子传输的时间依赖性治疗可预测物理上直观的结果，同时提供与时间无关的方法无法提供的见解。

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