The simulation of inhomogeneous liquid systems as micelles or of molecules near liquid interfaces is usually done with molecular dynamics (MD) simulations, requiring huge amounts of compute power and being limited by the accuracy of the force-field representation of the molecules. The COSMOmic method introduced an efficient and accurate alternative for the calculation of free energies of solutes in micellar system. Considering a micelle as layered liquid and starting from MD snapshots describing the atom probabilities in the layers, COSMOmic uses the COSMO-RS method in combination with a sampling of all conformational, positional and orientational states, constructs the partition function and derives the free energy of the solute in the micelle from its logarithm. COSMOmic is at least as accurate as MD simulations while requiring 10000 times less CPU power. But COSMOmic depends MD input, and thus is limited to solutes at infinite dilution in previously MD-simulated systems. COSMOmic is mainly applied to the prediction of distributions of neutral and ionic solutes between biomembranes and water and to the corresponding free energy profiles and permeabilities.<br/>By the simultaneous simulation of lateral pressure in the layers, the COSMOplex method overcomes this handicap and allows for the self-consistent prediction of self-organizing liquid systems, requiring nothing else than DFT/COSMO files as input. No additional approximations are made. The free energies of the molecules in such systems have about the same accuracy as the free energy predictions of COSMO-RS in homogeneous solvents, i.e. ~0.4 kcal/mol, compared to 0.9 kcal/mol for molecular dynamics simulations. COSMOplex requires 0.5 – 5 CPUh for a typical simulation, which is again four orders of magnitude faster than MD simulations. COSMOplex enables the efficient simulation and screening of pure and mixed micelles and biomembranes, of liquid-liquid, liquid-solid, and liquid-gas interfaces, and even of liquid crystals. First COSMOplex application to critical micelle concentrations and interfacial tensions will be shown, as well as one example demonstrating the simulation of the spontaneous 3-phase-splitting of an oil-surfactant-water system.

COSMO<i>plex</i>: A completely new paradigm for the self-consistent simulation of self-organizing liquid systems

256th National Meeting (2018)

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COSMOplex: A completely new paradigm for the self-consistent simulation of self-organizing liquid systems