[gmx-users] water can't freeze

[Wei, Xiupeng]

Hi gmx users,
         I'm a new Gromacs user. Till now, I can get pretty good simulation of ice melting to water, but why can't I simulate water freezing to ice?
         The .top and .gro files used for water freezing simulation are generated by ice melting to 310K. I changed the temperature in .mdp file to 230K, but after mdrun, the water was still water, it can't freeze?
         How can I get water freezing to ice?
        I paste mdp for your reference.
        Thanks.

best,
xiupeng


title                    = icing at 230 K with cuffoff
cpp                      = /lib/cpp
integrator               = md
;Time step
dt                       = 0.002
nsteps                   = 100000
;Output control
nstxout                  = 100000
nstvout                  = 100000
nstlog                   = 100
nstenergy                = 100
nstxtcout                = 100
;Neigbour searching
nstlist                  = 10
ns_type                  = grid
rlist                    = 0.8
;Non bonded interaction
coulombtype              = pme
optimize_fft             = yes
fourierspacing           = 0.2
pme-order                = 6
ewald-rtol               = 1e-05
rcoulomb                 = 0.8
vdw-type                 = Cut-off
rvdw                     = 0.8
DispCorr                 = EnerPres
;Temperature coupling
tcoupl                   = berendsen
tc-grps                  = System
tau_t                    = 0.1
ref_t                    = 230
;Pressure coupling
pcoupl                   = berendsen
pcoupltype               = isotropic
tau_p                    = 1.0
compressibility          = 5e-5
ref_p                    = 1.0

gen_temp                 = 230.0
constraints              = all-bonds
; generate velocities
gen_vel                  = yes
gen_seed                 = 173529