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#812 - 01/06/04 03:22 PM Pure repulsive VDW term
jfm17 Offline
Forum Member

Registered: 10/12/03
Posts: 6
I am attempting to reproduce a GROMOS force field that contains VDW terms given in the form (A/r**12) - (B/r**6). One atom type has B=0, giving a repulsive VDW term only. CHARMM has the form e(ij) [ (Rmin/r)**12 - 2(Rmin/r)**6 ], so usually it is not a problem to convert the A and B into epsilon(i,j) and Rmin, but how can I reproduce the term where B=0?

Thanks,
James Matthews

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#813 - 01/06/04 05:12 PM Re: Pure repulsive VDW term [Re: jfm17]
jb007 Offline
Forum Member

Registered: 09/30/03
Posts: 250
Loc: Florida State
Interesting question:
One way can be to set the attractive term = 0*(rmin/r)^6, which means that one can use the USERE-hookup in CHARMM for a user-energy defined potential. Have just begun to learn more about this facility, but see usage.doc

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