Effect of surface elasticity on the elastic response of nanoporous gold

In this work, the effect of surface elasticity on the effective elastic properties of nanoporous gold is studied. To this end, a theoretical framework for surface elasticity effects in submicron-sized solids is implemented as a user-defined finite element subroutine. This allows the use of the theory in large-scale engineering problems. The theory suggests a zero-thickness surface accommodating unique energetic properties and surface tension. For the example of ball-and-stick diamond cubic unit cell structures for nanoporous gold, it is shown that incorporation of surface excess elasticity and surface tension allows prediction of the size effect associated with the change of the surface area-to-volume ratio by capturing, e.g., the increase in the effective Young's modulus and decrease in the effective Poisson's ratio with decreasing ligament diameter, a phenomenon that is not accessible to classical continuum elasticity approaches.