[gmx-users] Density Differences

[Kavyashree M]

Dear gromacs users,

I am trying to simulate a 225aa protein at 300K in water,
with OPLSAA force filed, tip4p water model, using the
parameters below (for pressure equilibration) during
position restrained md.

integrator              = md
dt                      = 0.002
nsteps                  = 50000
nstcomm                 = 10
nstlist                 = 5
ns_type                 = grid
pbc                     = xyz
rlist                   = 1.40
coulombtype             = PME
rcoulomb                = 1.40
vdwtype                 = Switch
rvdw_switch             = 0.9
rvdw                    = 1.00
fourierspacing          = 0.12
pme_order               = 4
ewald_rtol              = 1e-5
optimize_fft            = yes
Tcoupl                  = nose-hoover
tc_grps                 = Protein  Non-Protein
tau_t                   = 0.4      0.4
ref_t                   = 300      300
nh-chain-length         = 1
gen_vel                 = no
continuation            = yes
constraints             = all-bonds
constraint-algorithm    = LINCS
lincs-order             = 4
lincs-iter              = 1
lincs-warnangle         = 30

when I calculate the densities, the average came out to be 1025.91 kg/m^3,
Could anyone please clarify me the reason for this density.

Thanking you
With regards
Kavya
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