The effect of vacancy defects on the electromechanical properties of monolayer NiTe 2 from first principles calculations.

The electromechanical properties of monolayer 1-T NiTe 2 under charge actuation were investigated using first-principles density functional theory (DFT) calculations. Monolayer 1-T NiTe 2 in its pristine form has a work area density per cycle of up to 5.38 MJ m -3 nm upon charge injection and it can generate a strain and a stress of 1.51% and 0.96 N m -1 , respectively. We found that defects in the form of vacancies can be exploited to modulate the electromechanical properties of this material. The presence of Ni-vacancies can further enhance the generated stress by 22.5%. On the other hand, with Te-vacancies, it is possible to improve the work area density per cycle by at least 145% and also to enhance the induced strain from 1.51% to 2.92%. The effect of charge polarity on the contraction and expansion of monolayer 1T-NiTe 2 was investigated. Due to its excellent environmental stability and good electromechanical properties, monolayer NiTe 2 is considered to be a promising electrode material for electroactive polymer (EAP) based actuators.