Before revision: In a continuum approach one can define a surface stress tensor that relates the work associated with the variation in , the total excess free energy of the surface due to the strain In general there is no change in area for shear, which means that and .
After revision: In a continuum approach one can define a surface stress tensor that relates the work associated with the variation in , the total excess free energy of the surface due to a strain tensor In general there is no change in area for shear, which means that for the second term on the right and , using the Kronecker delta .