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oai:figshare.com:article/32631159 2026-10-01T17:22:13Z portal_1172 item_type_8 month_year_10_2026

Determining the surface tension of gas-liquid interfaces through metadynamics Thomas Fyfe (24164253) PUREID: 235846484 Metadynamics free energy nucleation gas-liquid surface tension Lennard-Jones The measurement of surface tension γ provides information on the behaviour of phases at an interface. γ can be determined both experimentally and through computer simulation. Here, a gas-liquid interface is constructed and simulated in order to determine the value of gas-liquid interfacial surface tension γ_GL. In terms of the simulation protocol, the methodology used is molecular dynamics (MD) with well-tempered metadynamics for a one component simulation of Lennard-Jones Ar. The system operates in the NP_xxT ensemble with the simulation x-axis cell length L_x as the chosen collective variable (CV). This allows the system to transition from a pure liquid state to a coexistent gas-liquid state via cell expansion and vice versa via cell contraction multiple times over a typical simulation. The CV L_x is later converted to the total number of liquid atoms N_liq by way of a conservation relation. 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. 2026-10-01T17:22:13Z Text Thesis 10.17034/32631159.v1 https://figshare.com/articles/thesis/Determining_the_surface_tension_of_gas-liquid_interfaces_through_metadynamics/32631159 All Rights Reserved