标题： 基于[2,2]对环己烷的单分子结的热电优值的第一性原理计算 显示英文标题

标题： First-principles calculation of the thermoelectric figure of merit for [2,2]paracyclophane-based single-molecule junctions

摘要： 此处我们对通过基于{[}2,2{]}对-环烷烃的单分子结的热电输运进行了理论研究。结合从密度泛函理论 (DFT) 得到的电子和振动结构，以及非平衡格林函数技术，使我们能够在第一性原理层面上处理电子和声子输运特性。对于电子部分，我们包括了一个基于 DFT+$\Sigma$方法的近似自能修正。这使我们能够可靠地预测进入热电优值$ZT$的所有线性响应输运系数。对-环烷烃衍生物通过连接不同的功能基团可以极大地调节其化学性质。我们表明，对于特定分子，功能基团主要影响赛贝克系数，从而可以调节其符号和绝对值。我们预测，裸对-环烷烃的功能化会导致热电优值中电子贡献$Z_{\mathrm{el}}T$的大幅增强。然而，高的声子贡献会强烈抑制$ZT$。我们的工作证明了在对非共振分子输运结的$ZT$进行现实估计时，包括声子热导的重要性。此外，它展示了对一系列可用分子的热电性能进行化学调节的可能性，从而基于相同的分子框架实现性能相当的空穴和电子导电结。 显示英文摘要

摘要： Here we present a theoretical study of the thermoelectric transport through {[}2,2{]}para\-cyclo\-phane-based single-molecule junctions. Combining electronic and vibrational structures, obtained from density functional theory (DFT), with nonequilibrium Green's function techniques, allows us to treat both electronic and phononic transport properties at a first-principles level. For the electronic part, we include an approximate self-energy correction, based on the DFT+$\Sigma$ approach. This enables us to make a reliable prediction of all linear response transport coefficients entering the thermoelectric figure of merit $ZT$. Paracyclophane derivatives offer a great flexibility in tuning their chemical properties by attaching different functional groups. We show that, for the specific molecule, the functional groups mainly influence the thermopower, allowing to tune its sign and absolute value. We predict that the functionalization of the bare paracyclophane leads to a largely enhanced electronic contribution $Z_{\mathrm{el}}T$ to the figure of merit. Nevertheless, the high phononic contribution to the thermal conductance strongly suppresses $ZT$. Our work demonstrates the importance to include the phonon thermal conductance for any realistic estimate of the $ZT$ for off-resonant molecular transport junctions. In addition, it shows the possibility of a chemical tuning of the thermoelectric properties for a series of available molecules, leading to equally performing hole- and electron-conducting junctions based on the same molecular framework.