Theoretical studies of bond rupture and stability of molecular junctions

当单分子被认为是纳米尺度器件中的电子元件时，电流诱导的化学键断裂是一个主要问题。在这种情况下，研究最广泛的结构是分子结，其中单个分子与金属或半导体电极结合。分子结代表了一种独特的结构，可以在不同的非平衡状态下研究分子，并在更广泛的背景下研究纳米尺度下多体量子系统中电荷和能量传输的基本机制。该项目的目的是研究电流诱导的分子结中的键断裂过程，由传输电子与分子振动的耦合引起，以及它们对结稳定性的影响。为此，振动耦合电子传输在分子结的理论和方法将扩展到包括离解核势。具体而言，分层量子主方程方法将适用于此目的，它提供了一个非常准确的，在原则上数值精确的框架，研究在分子结中的电荷输运在一个完整的量子力学水平，包括非微扰和非马尔可夫效应。扩展的方法将被用来调查的基本机制，电流诱导的键断裂的分子结考虑模型范围从绝热到非绝热运输制度，包括非共振和共振运输的情况下，以及破坏性和非破坏性的解离。该方法，将在这个项目中开发，将提供重要的基准，以验证更近似的方法，也可以建立一个基础，对未来的应用程序，研究电流催化的化学反应。

Current-induced rupture of chemical bonds is a major concern when single molecules are being considered as electronic components in nano-scale devices. The most widely studied architecture in this context is a molecular junction, where a single molecule is bound to metal or semiconductor electrodes. Molecular junctions represent a unique architecture to investigate molecules in a distinct nonequilibrium situation and, in a broader context, to study basic mechanisms of charge and energy transport in a many-body quantum system at the nanoscale. The objective of this project is to investigate current-induced bond rupture processes in molecular junctions, caused by coupling of the transport electrons to the vibrations of the molecule, and their implications for the stability of the junctions. To this end, the theory and methodology of vibrationally-coupled electron transport in molecular junctions will be extended to incorporate dissociative nuclear potentials. Specifically, the hierarchical quantum master equation method will be adapted for this purpose, which provides a very accurate, in principle numerically exact framework to study charge transport in molecular junctions at a fully quantum mechanical level including nonperturbative and non-Markovian effects. The extended methodology will be used to investigate the fundamental mechanisms of current-induced bond rupture in molecular junctions considering models ranging from the adiabatic to the nonadiabatic transport regime, including nonresonant and resonant transport scenarios as well as destructive and nondestructive dissociation. The methodology, to be developed in this project, will provide important benchmarks to validate more approximate methods and can also build a basis towards future applications to study current-catalyzed chemical reactions.