eps(charmm)*4.184=epsilon(Gromacs)
0.15*4.184=0.6276
Rmin/2(Charmm)*2/(2^1/6)=sigma(Gromacs)
2.27*2/(2^(1/6))=0.404468(nm)
Cheers,
Jianhui
Date: Fri, 24 Sep 2010 15:55:44 +0200
From: "ABEL Stephane 175950" <stephane.a...@cea.fr>
Subject: [gmx-users] CHARMM -> gromacs epsilon and sigma conversiion
factors
To: <gmx-users@gromacs.org>
Message-ID:
<f654b3ee96986e4b8dc6ef0919c88da301038...@loderi.intra.cea.fr>
Content-Type: text/plain; charset="iso-8859-1"
Hi all,
I would like to add new atom types in the charmm27.ff for futures
simulations of glyolipids in water with gmx 4.5.1. I have finished to
convert the bonded in GROMACS format. However, I am little puzzled with the
vdW paramaters. I would like to know how to convert them (i.e. what are the
conversion factors used to convert the CHARMM sigma and epsilon parameters
to gromacs sigma and epsilon values ?).
For example for the chloride atom CLA
CHARMM 27
; atom ignored epsilon Rmin/2 ignored eps,1-4 Rmin/2,1-4
CLA 0.0 -0.150 2.27 ! chloride
GROMACS ffcharmmnb.itp
;name at.num mass charge ptype sigma epsilon
CLA 17 35.450000 -1.00 A 0.404468018036 0.6276
Thanks in advance for your help
Stefane
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