Engler-Schleyer force field

The Schleyer-Mislow program BIGSTRN (26b) likewise is extensively used. This program incorporates the so-called Engler-Schleyer force field (26a) as well as AUinger s 1971 force field as standard options and is unique in that it uses pattern-search methods of energy minimization. This method is effective at the outset but slows down as the geometry approaches a minimum (Table 2). 

Several modifications of the Engler-Schleyer force field have appeared. White (27) added olefin parameters and used an efficient two-stage Newton-Raphson minimization modification. The accuracy of the White force field regarding heat of formation calculations is... 

EAS (Engler, Andose, Schleyer) [184] is quite an old force field designed to model alkanes exclusively. The harmonic potential is used for the bond stretching and cubic anharmonic for the valence angle bending. No out of plane, electrostatic or cross terms are included. The nonbonded interactions are represented by the Buchingham potential. 

Engler, Andose, and Schleyer (18) used force field methods to predict the heats of formation of numerous polycyclic hydrocarbons experimental data on some of these compounds are now available. Table 2 summarizes this data and indicates the magnitude of the error expected in comparing predicted and experimental heats of formation for compounds of the type being considered. The agreement of calculated with experimental AH°fS is only fair ( 3 kcal mole" ) for both force fields, but experimental values often differed by a comparable... 

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