(13d) Force Field Parameters for Hydrogen, Oxygen, and Nitrogen to Study Complex Phase Equilibria and Interfacial Reactions

Authors: 
Wang, S., University of Colorado Boulder
Heinz, H., University of Colorado Boulder
Hydrogen, oxygen, and nitrogen play a vital role in phase equilibria and catalytic reactions like water splitting, fuel cells, and batteries. However, the dynamics of complex electrolyte and metal-solution-gas interfaces is difficult to monitor by imaging and spectroscopy. Molecular dynamics simulations are capable to provide missing insights and here we present new bonded potentials for O2, H2 and N2 as part of the Interface force field (IFF). A combination of harmonic bond stretching and Lennard-Jones parameters (with 12-6 and 9-6 options) is employed and the parameters are fully compatible with existing parameters for organic and inorganic compounds. The force field reproduces equilibrium bond lengths, vibrational features, liquid densities below the boiling point, vaporization energies, and solvation energies (Henry constants) in water at room temperature using standard water models (SPC, TIP3P) in quantitative (<1%) agreement with experimental measurements. The models thus reproduce chemical bonding, structures, and energies as required for a consistent Hamiltonian and significantly broaden the scope of simulation capabilities for gases and solid/liquid/gas electrolyte interfaces. The parameters can be added into many force fields including IFF, CVFF, PCFF, AMBER, CHARMM, OPLS-AA, COMPASS and GROMACS. The same parameterization protocol can also be applied to any other gas molecules.