CHARMM (Chemistry at HARvard Macromolecular Mechanics) is a force field for molecular dynamics as well as the name for the molecular dynamics simulation package associated with this force field.
The CHARMM Development Project involves a network of developers in the United States and elsewhere working with Martin Karplus and his group at Harvard to develop and maintain the CHARMM program. Licenses for this software are available, for a fee, to people and groups working in academia.
The commercial version of CHARMM, called CHARMm (note the lowercase 'm') is available from Accelrys
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