Validation of the general purpose QUANTA ®3.2/CHARMm® force field

TLDR

The study evaluates the CHARMm force field for small molecules, assessing its accuracy in reproducing experimental geometries. The authors analyzed 77 molecules, computing Cartesian and internal coordinate RMS deviations under varied force field conditions and computational techniques. The results confirm CHARMm’s internal consistency, with bond, angle, and dihedral RMS errors of 0.006 Å, 1.37°, and 3.2°, respectively, matching high‑quality electron diffraction data and outperforming comparable force fields. © 1992 by John Wiley & Sons, Inc.

Abstract

Abstract An evaluation of the CHARMm force field for small molecules is described. Using different force field conditions and computational techniques, a wide variety of compounds are analyzed. rms deviations of Cartesian coordinates for 49 diverse organic molecules taken from the Cambridge Crystallographic Data Base and internal coordinate geometries for 28 other molecules are reported. Results are described with different dielectrics, dihedral constraints, and crystal packing to allow analysis of deviations from experimental data and give precise statements of the reliability of the parameters used in the force field. Torsional barriers (rms = 0.4) and conformational energy differences (rms = 0.4) are examined and comparisons made to other force fields such as MM2, Tripos, and DREIDING. The results confirm that CHARMm is an internally consistent all purpose force field with energy terms for bonds, angles, dihedrals, and out‐of‐plane motions, as well as nonbonded electrostatic and van der Waals interactions. Reported CHARMm results (rms = 0.006 Å for bonds, rms = 1.37° for angles, and rms = 3.2° for dihedrals) are in excellent agreement with high quality electron diffraction data. © 1992 by John Wiley & Sons, Inc.