On 4/06/2012 3:46 AM, ramesh cheerla wrote:
Dear Gromacs experts,

I am planing to use tabulated potentials for dihedral functional form Summn over 'n' 0.5*K [ ( Cos n(phi-phi0)] , Here 1<= n <= 3 . I have three different K values (i.e K1,K2,K3 ) one for each 'n' value ( Here 'n' is multiplicity).

You do not need a table for this - type 9 will do the job easily, and for friendly values of phi0, there exists an equivalent form to the above that can be expressed as a Ryckaert-Belleman dihedral. See various places of manual chapters 4 and 5.

I have generated table and given the table number in dihedrals directive of the ffbonded.itp file, According to my understanding one has to supply K ( force constant ) value in addition to table number in topology. In my case I have three different "K" values, which "k" value do I have to take, Can I take sum of all the three "k" values or can I take arbitrary value.

Your table would need to be the weighted sum of the three cosines, so apparently you have not yet generated such a table. But rather than buy trouble, go and do the easier and faster solutions above :-)

Mark
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