Can the Lennard–Jones 6‐12 function replace the 10‐12 form in molecular mechanics calculations?

A protocol to replace “10‐12” hydrogen bonding function with the “6‐12” form to reproduce hydrogen bond distances, energies, and geometries in molecular mechanics calculations is described. The 6‐12 function was least‐squares fit to the normally employed 10‐12 form of the function for the hydrogen bond types of the Weiner et al. force field by iterating over the A and B coefficients. A weighting function was used to fit the curves in the most critical areas. The 6‐12 hydrogen bond model was compared with the Weiner et al. force field, OPLS/AMBER fore field, and quantum mechanical calculations on two simple systems, the water dimer and the chloride‐water interaction. The 6‐12 model produced structures, energies, and geometries that were consistent with the other molecular mechanics calculations and showed reasonable agreement to the quantum mechanical results for the water dimer. The 6‐12 model was also compared with normal calculations using a 10‐12 model on several representative systems. The results indicate that the 6‐12 function, when substituted by the procedure outlined in this work, yields structures and hydrogen bond properties that are similar to the normal 10‐12 model.