The Shape of Aerosol-OT Reverse Micelles and the Impact of Force Field

Aerosol-OT (AOT) reverse micelles are ideal systems for the study of nanoconfinement with molecular dynamics (MD) simulations often serving as a useful way to gain molecular level understanding of the system. In the present study, we examine the impact of the force field on the behavior of the simulated AOT reverse micelles and benchmark the results. We simulated w₀=5 reverse micelles using the CHARMM force field and three variations on the OPLS-AA force field. We benchmark the system against experimental values for the dipole moment, the relaxation constant of the complex permittivity, and the quasi-elastic neutron scattering spectrum. We evaluate the eccentricity and convexity as well as local curvature of the reverse micelle to assess how the force field impacts various values. We find that the force field has a large impact on the eccentricity of the micelle despite all force fields tested recreating the experimental dipole moment well. Our eccentricity results also report a surprisingly high abundance of oblate ellipsoidal shaped micelles not reported in previous literature. These results highlight the importance of testing the force fields for accuracy in order to obtain correct molecular level insight into the system.