AN IMPROVED EMPIRICAL FORCE-FIELD FOR SATURATED-HYDROCARBONS

A new molecular mechanics force field for alkanes is presented. The force field aims to eliminate some identified failures of the well‐known MM2 force field. The new energy function gives an improved prediction of the rotational barriers of highly congested molecules, a better calculation of short nonbonded contacts, and the correct reproduction of bond elongation in small torsion angles. The calculation of sublimation enthalpies is also improved. The standard deviation of the formation enthalpies for a set of 54 compounds is 0.63 kcal/mol; this compares with the reported value of 0.42 calculated with MM2 and MM3 for different sets. The force field parameters were obtained using a least squares method. Copyright © 1990 John Wiley & Sons, Inc.