Improved ReaxFF Force Field Parameters for Au–S–C–H Systems

Evaluation and reparameterization of previously reported ReaxFF parameters (Järvi, T. T.; et al. J. Phys. Chem. A 2011, 115, 10315–10322) is carried out for Au–S–C–H systems. Changes in Au–S and Au–Au bond parameters and S–Au–S angle bending parameters yield improvements for bond bending potential energy surfaces. The new ReaxFF parameters lead to good agreement with density functional theory geometries of small clusters and gold–thiolate nanoparticles. The energies of Au38(SCH3)24 clusters are compared, and the new ReaxFF calculations are also in good agreement with PBE calculations for the isomer orderings. In addition, the relative energies of Au40(SCH3)24 nanoparticles and Au-thiolate SAMs are calculated using the updated parameters. These new ReaxFF parameters will enable the study of the geometries and reactivity of larger gold–thiolate nanoparticles.