Dear Ashima

the deformation potential is defined and easly calculated in the case of 3D materials under strain (hydrostatic pressure for example) and is related to the change of electronic properties of the material in interest (Eg) with volume change. so, we can do the same thing for 2D structure but by using S(surface) rather than V (volume) but i'm not sure that we can call it deformation potential perhaps we shouls call it 2D deformation potential. if this what you would, you can calculate the change in the bandgap change of your structure versus the a parameter. 

Thank you Sir , for your suggestion.