An empirical method to determine the free surface energy of solids at different deformations and temperature regimes: An application to Al

We have performed molecular dynamics (MD) simulations using the three low index surfaces of Al to determine the variation of the surface energy as a function of deformation and temperature. We have also developed an empirical formulation for the surface free energy as a function of deformation. The observed difference between the numerical and analytical results has led us to divide the deformation into a mechanical and a thermal contribution. From this observation, we have obtained an expression for the surface free energy placing the temperature dependence on the bulk and surface elastic constants. Our simulations permitted us to analyze the multilayer relaxation for the particular surfaces studied. Namely, we found the first atomic layer of the Al(1 0 0) surface to be in slight contraction, an alternation between contraction and expansion in the first atomic layers of the Al(1 1 0) surface and slight expansion in the first atomic layer of the Al(1 1 1) surface.