MCCCS Towhee (SKS)



    This section covers the Smit-Karaborni-Siepmann Force Field (SKS) for n-alkanes as it is implemented into the towhee_ff_SKS file in the ForceFields directory. All of the Towhee atom types for this force field are listed, along with a short description of their meanings. SKS uses a 'Lennard-Jones' classical_potential and the 'Lorentz-Berthelot' classical_mixrule. This forcefield is best used with a 13.8 Angstrom cutoff with no tail corrections and without shifting at the cutoff. This strange set of parameters is due to a bug in the code originally used to produce this forcefield. Please see the Erratum in the references section for more information. The SKS forcefield was later extended to branched alkanes (SMMK Main) and eventually replaced by the TraPPE-UA force field. Any discrepencies (especially typos) from the published force field values are the sole responsibility of Marcus G. Martin, and I welcome feedback on how this implementation compares with other programs.
References for SKS
    The parameters and detailed results for the SKS force field are found here. Please note that an error was made in the code that produced the results in that paper that essentially meant that tail corrections were not employed. Please see the following erratum for more information.
SKS in Towhee
    The official force field name for SKS in Towhee is 'SKS'. Here I list all of the atom names for use in the towhee_input file, along with a brief description. Please note that the capitalization and spacing pattern is important and must be followed exactly as listed here.
    • 'CH3' methyl group (C plus 3 bonded H as a united-atom) on an n-alkane of C4 or longer.
    • 'CH2' methylene group (C plus 2 bonded H as a united-atom) on an n-alkane of C4 or longer.
Coulombic interactions
    There are no coulombic interactions for this force field.
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Send comments to: Marcus G. Martin
Last updated: September 07, 2005