Force field
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Force fields are applicable to several categories.
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Physics
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.
A force field can exist in the surrounding space of a mass, electric charge, or magnet, so that something new brought to the environment will experience a force.
Examples of force fields
Chemistry
In the context of molecular modelling, 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 electron 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 -
- 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
- MM2, MM3, MM4 - developed by Norman L. Allinger, for a broad range of chemicals
Sci-fi
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.
Research and Development
In reality, scientists and physicists are working with the US army to develop a new range of technologies to be used in combat. These include a high powered laser weapon which could be fitted to tanks or other combat vehicles as well as an electromagnetic force field which would wrap around an object and deflect incomming bullets. The technology is far from ready, but the fact that it has been tested and researched means that sci-fi fans may not have to wait long before psy-cannons and force-fields are a reality.