中文摘要：

使用一个空间地对称的 phenyldithiolate 分子作为模型系统并且通过从对称的接触地点转移一个电极形成不对称的接触在二个金电极之间夹了，我们在如此的一台设备调查了电子运输的性质由第一原则。一台设备的 I (G)-1/characteristics 证明重要不对称现象和电流和传导力的大小在二接触之一显著地取决于分子金属距离的变化，这被发现。也就是，不对称的接触将在一台分子的设备的当前电压的特征上导致弱修正效果。当偏爱电压是内在的起源时，分析证明 HOMO 由于收费设备为反响的通道和它的移动负责不对称我(G)-Vcharacteristics。

英文摘要：

Using a spatially symmetric phenyldithiolate molecule sandwiched between two gold electrodes as model system and through shifting one electrode from symmetric contact site to form asymmetric contact, we investigated the properties of electronic transport in such a device by the first-principles. It was found that the/（G ）-V characteristics of a device show significant asymmetry and the magnitudes of current and conductance depend remarkably on the variation of molecule-metal distance at one of the two contacts. Namely, an asymmetric contact would lead to the weak rectifying effects on the current-voltage characteristics of a molecular device. The analysis shows that the HOMO is responsible for the resonant tunneling and its shift due to the charging of the device while the bias voltage is the intrinsic origin of asymmetric/（G）- Vcharacteristics.