In general physics, a force field is a vector field representing the gradient of a potential. The vectors that are the values of a force field are forces, and so measured in units of force such as newtons and pounds-force.
In the context of molecular dynamics, a force field (also called a forcefield) is a more loosely defined term and refers to the functional form and parameter sets used to describe the interactions (potential, forces) within a system of particles (atoms or similarly sized objects). It is independent of the system's configuration and is not a numerical field as in the above context.
A force field can be empirical, derived from higher-level modelling (e.g. quantum chemical studies), or even heuristic.
Some popular forcefields and the types of molecules they can be applied to include:
Classical forcefields:
- AMBER - widely used for proteins and DNA
- CHARMm - originally developed at Harvard, widely used for both small molecules and macromolecules
- CVFF - also broadly used for small molecules and macromolecules
- GROMACS -
- GROMOS -
- MM2, MM3, MM4 - developed by Norman L. Allinger, for a broad range of chemicals
- OPLS, OPLSAA - developed by William L. Jorgensen
Second-generation forcefields:
- CFF - a family of forcefields adapted to a broad variety of organic compounds, includes forcefields for polymers, metals, etc.
- MMFF - developed at Merck, for a broad range of chemicals
In science fiction and fantasy literature, a force field is a physical barrier made up of energy to protect a person or object from attacks or intrusions. The plasma window is a real-life technology that partially recreates the functionality of a force field, providing a separation between vacuum and gas that allows some radiation and energetic particles to pass through.
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