Abstract We present an ab initio method to calculate elastic quantum transport at the nanoscale. The method is based on a combination of density functional theory using plane wave nonlocal pseudopotentials and the use of auxiliary periodic boundary conditions to obtain the scattering states. The method can be applied to any applied bias voltage and the charge density and potential profile can either be calculated self-consistently, or using an approximated self-consistent field (SCF) approach. Based on the scattering states one can straightforwardly calculate the transmission coefficients and the corresponding electronic current. The overall scheme allows us to obtain accurate and numerically stable solutions for the elastic transport, with a computational time similar to that of a ground state calculation. This method is particularly suitable for calculations of tunneling currents through vacuum, that some of the nonequilibrium Greens function (NEGF) approaches based on atomic basis sets might have difficulty to deal with. Several examples are provided using this method from electron tunneling, to molecular electronics, to electronic devices: (i) On a Au nanojunction, the tunneling current dependence on the electrode–electrode distance is investigated. (ii) The tunneling through field emission resonances (FERs) is studied via an accurate description of the surface vacuum states. (iii) Based on quantum transport calculations, we have designed a molecular conformational switch, which can turn on and off a molecular junction by applying a perpendicular electric field. (iv) Finally, we have used the method to simulate tunnel field-effect transistors (TFETs) based on two-dimensional transition-metal dichalcogenides (TMDCs), where we have studied the performance and scaling limits of such nanodevices and proposed atomic doping to enhance the transistor performance.

中文翻译：

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使用平面波的从头算量子输运计算

摘要 我们提出了一种从头计算的纳米级弹性量子传输方法。该方法基于使用平面波非局部赝势的密度泛函理论和使用辅助周期边界条件来获得散射状态的组合。该方法可以应用于任何施加的偏置电压，电荷密度和电位分布可以自洽计算，也可以使用近似自洽场 (SCF) 方法计算。基于散射状态，可以直接计算传输系数和相应的电子电流。总体方案使我们能够获得准确且数值稳定的弹性输运解，其计算时间类似于基态计算的计算时间。这种方法特别适用于计算穿过真空的隧道电流，一些基于原子基组的非平衡格林函数 (NEGF) 方法可能难以处理。使用这种方法提供了几个例子，从电子隧道到分子电子学，再到电子器件：（i）在 Au 纳米结上，研究了隧道电流对电极 - 电极距离的依赖性。(ii) 通过对表面真空状态的准确描述来研究通过场发射共振 (FER) 的隧穿。(iii) 基于量子传输计算，我们设计了一种分子构象开关，它可以通过施加垂直电场来打开和关闭分子结。(iv) 最后，