ForceField Menu

This menu contains commands that

MMX: Use the MMX force field

MM3: Use Allinger's MM3 (1996) force field

MMFF94: Use Halgren's MMFF94 force field

OplsAA: Use Jorgenson's OplsAA force field

United Atom: Use a united atom force field developed for Pcmodel based on the functional form of OplsUA

MMX

The MMX force field is based on Allinger's MM2 force field (QCPE-395, 1977) with the pi-Vescf routines taken from MMPI (QCPE 318) also developed by Allinger. John McKelvey of Kodak modified the pi-Vescf routines for open shell species, while J.J. Gajewski of Indiana University made changes to the Heat of Formation calculations. MMX increased the number of atom types over MM2 as well as adding the ability to treat transition metals and transition states. The transition metal changes have been retained in version 10 but not the transition state changes.

MM3

The MM3 force field implements Allinger's MM3 force field parameters and functions as given in:

N. L. Allinger, Y. H. Yuh and J.-H. Lii, "Molecular Mechanics.The MM3 Force Field for Hydrocarbons. 1", J. Am. Chem. Soc., 111, 8551-8566 (1989)/

The current parameter set downloaded from Professor Allinger's lab in 1996.

MMFF94

The MMFF94 force field implements Halgren's MMFF94 force field parameters and functions as given in a series of papers published in the Journal of Computational Chemistry in 1996.



OplsAA

The OplsAA force field implements Jorgenson's OplsAA force field parameters and functions as given:

W. L. Jorgensen, D. S. Maxwell and J. Tirado-Rives, "Development and Testing of the OPLS All-Atom Force Field on Conformational

Energetics and Properties of Organic Liquids", J. Am. Chem. Soc., 117, 11225-11236 (1996)

D. S. Maxwell, J. Tirado-Rives and W. L. Jorgensen, "A Comprehensive Study of the Rotational Energy Profiles of Organic Systems by Ab Initio

MO Theory, Forming a Basis for Peptide Torsional Parameters", J. Comput.Chem, 16, 984-1010 (1995)

W. L. Jorgensen and N. A. McDonald, "Development of an All-Atom Force Field for Heterocycles. Properties of Liquid Pyridine and Diazenes",

THEOCHEM-J. Mol. Struct., 424, 145-155 (1998)

N. A. McDonald and W. L. Jorgensen, "Development of an All-Atom Force Field for Heterocycles. Properties of Liquid Pyrrole, Furan,

Diazoles, and Oxazoles", J. Phys. Chem. B, 102, 8049-8059 (1998)

R. C. Rizzo and W. L. Jorgensen, "OPLS All-Atom Model for Amines: Resolution of the Amine Hydration Problem", J. Am. Chem. Soc.,

121, 4827-4836 (1999)

United Atom

The United Atom force field implements a simple untied atom force field similar in functional form to OplsUA with parameters derived from various sources. It was developed to model large hydrocarbons with the elements of C,H,N,O and S. Hydrogens are only attached to O,N and S and all CH groups are treated as united atoms. It has been used to provide an initial optimization of organic polymers of greater than 10,000 atoms prior to the application of all atom force fields in molecular dynamics simulations using LAMMPS. See the file oplsua.prm for a definition of the atom types current implemented.