Vibrational properties and phonon transport of nanobridges (A08*)

我们将研究如何通过温度和机械应力来调节纳米桥的振动特性。发展一个基于密度泛函理论的从头计算描述，我们将包括非谐效应，以考虑它们对声子及其波动的热流的影响。在这种方法，允许确定声子寿命的基础上声子-声子散射，我们将专注于分子和原子尺度的结。我们将探讨声子输运对分子形状、共轭、锚定基团、取代基和电极材料的依赖性，以及通过破坏性声子干涉和增加非谐性来抑制热导的方法。最后，使用分子动力学和力场，从头算方法校准，我们将探索一种新型的热二极管，利用不同的热膨胀系数，以实现高整流比。

We will study how vibrational properties of nanobridges can be tuned through temperature and mechanical stress. Developing an ab-initio description based on density functional theory, we will include anharmonic effects to consider their influence on the heat current by phonons and its fluctuations. Within this methodology that allows to determine phonon lifetimes based on phonon-phonon scattering, we will focus on molecular and atomic scale junctions. We will explore the dependence of phonon transport on molecular shape, conjugation, anchoring groups, substituents and electrode materials as well as ways to achieve a suppression of thermal conductance through destructive phonon inter-ference and increased anharmonicities. Finally, using molecular dynamics and force fields, calibrated with the ab-initio approach, we will explore a new type of thermal diode that exploits different thermal expansion coefficients to achieve a high rectification ratio.