Figure 3
The mechanical response of tinselenidene under uniaxial strain along x (a) and y (b) directions.
Strain is defined as 
, where 
represent the lattice parameters (thickness for 
) along x, y, z directions under strain, respectively and 
are the corresponding original lattice constants (thickness for 
) without strain. The positive (or negative) s means a tensile (or compressive) strain, while 
corresponds the case without strain. The Poisson’s ratio can be obtained by fitting 
, where t is the strain along the x or y direction and 
could be regarded as the Poisson’s ratio. The corresponding stress-strain relations in x and y directions are shown in the upper right insets.
