Structural evolution and the role of native defects in subnanometer MoS nanowires

We carried out first-principles calculations based on density functional theory aiming to understand the structural evolution along the stretching process and the impact of native defects in metallic subnanometer MoS nanowires (NWs). By pulling the pristine NWs quasistatically, we investigate the full structural evolution along the stretching process until the nanowire breaking point, obtaining a maximum applied stress (force) of $\ensuremath{\approx}18.9$ GPa (7.1 nN). On the other hand, since the existence of intrinsic defects is likely to occur in these samples, we show that under S-rich conditions a sulfur antisite is found to be the energetically most stable defect, and under Mo-rich conditions a sulfur vacancy has the lowest formation energy. Our results also reveal that these defects present local reconstruction that can be clearly identified by the simulated scanning tunneling microscopy images. Furthermore, through a detailed analysis of the electronic structure, we verify that with the exception of the Mo interstitial and S antisite, all defects preserve the metallic behavior of the MoS nanowires.