MCCCS Towhee (Hard Sphere)



    This section covers Hard Sphere parameters as they are implemented into the towhee_ff_HardSphere file in the ForceFields directory. It is a bit strong to call this a force field, as all there is to the hard spheres is a series of sigma values, but this explains how to use the builder with the hard sphere potentials, and how to add in any other hard sphere diameters that you might want to use in a simulation.


Hard Spheres in Towhee
    The official force field name for Hard Spheres in Towhee is 'HardSphere'. Here I list all of the Hard Sphere atom names currently in use for the towhee_input file, along with a brief description (although the meaning of the atom names should be obvious). If you want to add any new hard sphere diameters into Towhee just take a look in the ffhardsphere.F subroutine. Search for one of the atom types listed below and you will find the complete listing of hard sphere parameters. It should be obivous how to add new atom diameters from the examples. Please note that the capitalization and spacing pattern is important and must be followed exactly as listed here.
    • 'hs0.0' : hard sphere with 0.0 diameter. This is essentially an ideal atom, but it is still excluded from being inside of other atoms. Thus it is a hard point potential.
    • 'hs0.5' : hard sphere with 0.5 diameter.
    • 'hs1.0' : hard sphere with 1.0 diameter.
Coulombic interactions
    It is possible to combine the hard sphere potential with point charges. Simply assign the point charges to the atoms as you see fit.
Improper torsions
    There are no improper torsions set up specifically for hard spheres.
    There are no features to build proteins out of hard spheres.
Return to the Towhee Capabilities web page


Send comments to: Marcus G. Martin
Last updated: September 07, 2005