In the context of molecular modeling, a force field (a special case of energy functions or interatomic potentials; not to be confused with force field in classical physics) refers to the functional form and parameter sets used to calculate the potential energy of a system of atoms or coarse-grained particles in molecular mechanics and molecular dynamics simulations. The parameters of the energy functions may be derived from experiments in physics or chemistry, calculations in quantum mechanics, or both.
All-atom force fields provide parameters for every type of atom in a system, including hydrogen, while united-atom interatomic potentials treat the hydrogen and carbon atoms in each methyl group (terminal methyl) and each methylene bridge as one interaction center. Coarse-grained potentials, which are often used in long-time simulations of macromolecules such as proteins, nucleic acids, and multi-component complexes, provide even cruder representations for higher computing efficiency. By calculating all the energies (bond, angle, torsion, electrostatic, VDW, etc.), the analytical first and second derivatives of each atom in a biological system, we can simulate how each atom moves in a system, the chemical reaction path, spectra, correlation of structure and function.
Warshel and his colleagues, Levitt and Lifson, developed the Consistent Force Field (CFF) method    and the corresponding computer programs that are the basis of current molecular modeling methods (CHARMM, AMBER, GROMOS, etc.).
MOLARIS, which has been evolved from Warshel's initial computer program, is a package that integrates two main modules, ENZYMIX and POLARIS, and a set of general utilities which are incorporated in the module ANALYZE. These three modules are interconnected in order to provide a robust and powerful tool for investigating the function of biological molecules. The program is particularly effective in studies of enzymatic reactions  and in evaluating electrostatic energies in proteins . MOLARIS-XG is an extension of the MOLARIS package to coarse-grain (CG) calculations .
MOLARIS can be used as a complete tool for the investigation of the structure-function relationships in enzymes and other biomolecules. It has also been used for: