Microscopic expressions for the rigidity constants of a simple liquid–vapor interface

Abstract

We present microscopic equations for the rigidity constants of a simple liquid–vapor interface. These expressions are analogous to the Kirkwood–Buff formula for the surface tension. The rigidity constants are calculated using an approximate expression for the density auto correlation function in the interface near the critical point. This results in k=0.631 kBTc and k=0.239 kBTc.