Force field MMFFs MMFF94,MMFF

The Merck molecular force field (MMFF) is one of the more recently published force fields in the literature. It is a general-purpose method, particularly popular for organic molecules. MMFF94 was originally intended for molecular dynamics simulations, but has also seen much use for geometry optimization. It uses five valence terms, one of which is an electrostatic term, and one cross tenn. 

Halgren, T. A. (1999) MMFF VII. Characterization of MMFF94, MMFF94s, and other widely available force fields for conformational energies and intermolecular-interaction energies and geometries. J. Comput. Chem. 20, 730-748. 

Molecular mechanics models differ both in the number and specific nature of the terms which they incorporate, as well as in the details of their parameterization. Taken together, functional form and parameterization, constitute what is termed a force field. Very simple force fields such as SYBYL, developed by Tripos, Inc., may easily be extended to diverse systems but would not be expected to yield quantitatively accurate results. On the other hand, a more complex force field such as MMFF94 (or more simply MMFF), developed at Merck Pharmaceuticals, while limited in scope to common organic systems and biopolymers, is better able to provide quantitative accounts of molecular geometry and conformation. Both SYBYL and MMFF are incorporated into Spartan. 

MMFF is a good small-molecule force field. Gundertofte et al. have shown that MMFF93, MMFF94 s immediate... 

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