Dear gromacs users,
I am trying to convert a charmm style parameter file into gromacs. So I al
trying to understand how converting the force constants from CHARMM to
gromacs.
Using the CHARMM27 force field as a reference, I've noticed that to convert
the bond constant the following formula is supposed to be used:
k_gromacs = k_charmm**4184**2
In fact if I try to convert the following line from
par_all27_prot_lipid.prm charmm file:
CEL1 CEL1 440.000 1.340 ! butene, yin,adm jr., 12/95
I obtain the right result ( 440.000*4184*2. = 368192.0)
charmm27/ffbonded.itp CEL1 CEL1 1 0.134 368192.0
But to convert the angle constants I've to use the following formula:
k_gromacs = k_charmm**4.184**2.
how demostrated by the conversion of the following line:
par_all27_prot_lipid.prm CEL1 CEL1 CTL2 48.00 123.50 ! from
2-butene, yin,adm jr., 12/95
into
charmm27/ffbonded.itp CEL1 CEL1 CTL2 5 123.50 401.664 0.0
0.0
My question is:
Why in the former case I need the constant 4184 while in the latter the
constant 4.184 is supposed to be used? Am I miss something?
--
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