Determining the surface tension of gas-liquid interfaces through metadynamics

This simulation protocol allows for the construction of a free energy profile with respect to N_liq, from which the free energy change ΔG associated with interface formation can be found and consequently the thermodynamic definition for γ_GL can be calculated. This work assesses the viability of this new method by investigating scaling in pairwise cutoff size r_c, interfacial surface area A and reduced temperature T^*.

In particular, with MD parameters of r_c = 7 σ, A = 16 σ x 16 σ for T^* = 0.9, 0.95, 1.0, the obtained values of γ_GL relative to experiment are in very good agreement and have average deviations of 4.1%, 1.6% and <0.1% respectively when compared to experimental γ_GL values. Further work in studying this method can investigate a wider range of reduced temperatures T^*, different systems such as water, different interface geometries and multi component systems.