Refining Nonequilibrium Moves in Monte Carlo Simulations
The stationary phase in supercritical fluid chromatography contains carbon dioxide interacting with capping silanes on silica. Analytes dissolved in carbon dioxide also interact with the silanes. Classic Monte Carlo moves within Gibbs ensembles model carbon dioxide well. Silane interactions with other silanes and with carbon dioxide, however, are more troublesome. Nonequilibrium pulling and compression moves may help simulations explore fully the configuration space of the capping silanes and of solutes. Two non-equilibrium methods that will be used are Jarzynski-equation-type pulling simulations for solutes and silanes, and nonequilibrium candidate Monte Carlo moves for silanes. Refinement of the silane force field will continue concurrently will developing the new moves. Calculations at MSI will test new code, refine force-field parameters, and collect data for equilibrium properties.
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