Dear all,
I performed simple simulations of TIP4P-Ew water for 500 ps with three
different GROMACS versions, namly 3.2.1, 3.3.1 and 4.0.2. There are 1000
molecules in the box and the temperature was 303 K at 1 bar. When I
compare the total energies of the three equilibrated simulations I get:
-38642.4 for GROMACS 4.0.2
-38638.2 for GROMACS 3.3.1
-38491.5 for GROMACS 3.2.1
So the 3.2.1 energies deviate by ca 150 kJ/mol from the other two. If I
completly switsh off the coulomb interactions all energies are the same.
Does anyone know a reason for that? I don't find anything about the
3.2.1 version at the web site.
regards
My top file and mdp files look like:
[ defaults ]
; nbfunc comb-rule gen-pairs fudgeLJ fudgeQQ
1 2 yes 0.5 0.8333
[ atomtypes ]
;name mass charge ptype c6 c12
ow 15.99940 0.00000 A 0.31643 0.68096
hw 1.00790 0.52422 A 0.00000 0.00000
vw 0.00000 -1.04844 A 0.00000 0.00000
[ nonbond_params ]
; i j func c6 c12
ow hw 1 0.000000E+00 0.000000E+00
ow vw 1 0.000000E+00 0.000000E+00
hw vw 1 0.000000E+00 0.000000E+00
[ moleculetype ]
; molname nrexcl
SOL 1
[ atoms ]
; nr type resnr residue atom cgnr charge mass
1 ow 1 SOL ow 1 0.0 15.99940
2 hw 1 SOL hw 1 0.52422 1.00800
3 hw 1 SOL hw 1 0.52422 1.00800
4 vw 1 SOL vw 1 -1.04844 0.0
[ settles ]
; ow funct doh dhh
1 1 0.09572 0.15139
[ dummies3 ]
; Dummy from funct a b
4 1 2 3 1 0.1066767208 0.1066767208
[ exclusions ]
1 2 3 4
2 1 3 4
3 1 2 4
4 1 2 3
[ system ]
; Name
Converted from moscito
[ molecules ]
; Compound #mols
SOL 1000
and
title = Yo
cpp = /lib/cpp
dt = 0.002
nsteps = 250000
nstcomm = 1
nstxout = 0
nstvout = 0
nstxtcout = 100
nstlog = 10000
nstenergy = 100
nstlist = 6
ns_type = grid
coulombtype = pme
fourierspacing = 0.12
pmeorder = 4
optimize_fft = yes
ewald_rtol = 1.0e-5
DispCorr = EnerPres
constraint_algorithm= lincs
lincs_order = 4
lincs_iter = 3
lincs-warnangle = 30
rlist = 0.9
rvdw = 0.9
rcoulomb = 0.9
Tcoupl = nose-hoover
tc-grps = sol
ref_t = $T
tau_t = 0.5
Pcoupl = parrinello-rahman
Pcoupltype = isotropic
tau_p = 2.0
compressibility = 33.0e-6
ref_p = 1.0
gen_vel = no
;gen_temp = 303
;gen_seed = 1993
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