[gmx-users] Tabulated potentials for dihedrals - regd
Mark Abraham
Mark.Abraham at anu.edu.au
Mon Jun 4 09:25:58 CEST 2012
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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