Mechanical stabilities and nonlinear properties of monolayer Gallium sulfide under tension

The mechanical stabilities and nonlinear properties of monolayer Gallium sulfide (GaS) under tension are investigated using density functional theory (DFT). The ultimate stresses and ultimate strains, and the structure evolutions of monolayer GaS under armchair, zigzag, and equiaxial tensions are predicted. A thermodynamically rigorous continuum description of nonlinear elastic response is given by expanding the elastic strain energy density in a Taylor series in Lagrangian strain truncated after the fifth order term. Fourteen nonzero independent elastic constants are determined by least-square fit to the OFT calculations. Pressure dependent elastic constants (C-ij(P)) and pressure derivatives of C-ij(P) (C-ij') are also calculated. Calculated values of ultimate stresses and strains, and the in-plain Young's modulus are all positive. It proves that monolayer GaS is mechanically stable. (C) 2014 Elsevier Ltd. All rights reserved.