TraPPE-zeo: Transferable Potentials for Phase Equilibria Force Field for All-Silica Zeolites

The transferable potentials for phase
equilibria (TraPPE) force
field is extended to all-silica zeolites. This novel force field is
parametrized to match the experimental adsorption isotherms of n-heptane, propane, carbon dioxide, and ethanol with the
Lennard-Jones parameters for sorbate–framework interactions
determined in a consistent manner using the Lorentz–Berthelot
combining rules as for other parts of the TraPPE force field. The
TraPPE-zeo force field allows for accurate predictions for both adsorption
and diffusion of alkanes, alcohols, carbon dioxide, and water over
a wide range of pressures and temperatures. In order to achieve transferability
to a wider range of molecule types, ranging from nonpolar to dipolar
and hydrogen-bonding compounds, Lennard-Jones interaction sites and
partial charges are placed at both the oxygen and the silicon atoms
of the zeolite lattice, which allows for a better balance of dispersive
and first-order electrostatic interactions than is achievable with
the Lennard-Jones potential used only for the oxygen atoms. The use
of the Lorentz–Berthelot combining rules for unlike interactions
makes the TraPPE-zeo force field applicable to any sorbate as long
as the relevant TraPPE sorbate–sorbate parameters are available.
The TraPPE-zeo force field allows for greatly improved predictive
power compared to force fields that explicitly tabulate the individual
cross-interaction parameters.