On the effect of vacancy defect on the mechanical properties of gallium nitride nanosheets

Using molecular dynamics (MD) simulations, the influence of the vacancy defects on the mechanical properties of gallium nitride (GaN) nanosheets is investigated. Two types of defective nanosheets are studied. In one of them, only one atom is removed at the vacancies and in the other, the number of removed atoms is not limited. It is shown that GaN nanosheets with multiple vacancies have larger in-plane elastic modulus than nanosheets with single vacancies. Besides, the ultimate stress and strain of GaN nanosheets are computed. Compared to perfect nanosheet, a significant decrease is observed in the ultimate stress of GaN nanosheet with only 2% defect. By plotting the fracture evolution of nanosheets under uni-directional tensile loading, three different patterns are observed. Moreover, by using bi-directional tensile tests on the nanosheets, the bulk moduli of perfect and defective GaN nanosheets are computed.