New out-of-plane angle and bond angle internal coordinates and related potential energy functions for molecular mechanics and dynamics simulations

With currently used definitions of out-of-plane angle and bond angle internal coordinates, Cartesian derivatives have singularities, at "pr2 in the former case and p in the latter. If either of these occur during molecular mechanics or dynamics simulations, the forces are not well defined. To avoid such difficulties, we provide new out-of-plane and bond angle coordinates and associated potential energy functions that inherently avoid these singularities. The application of these coordinates is illustrated by ab initio calculations on ammonia, water, and carbon dioxide. Q 1999 John Wiley & Sons, Inc. J Comput Chem 20: 1067]1084, 1999