Hello everyone,
I use the TIP4P-2005 water model to simulate the two-phase process of water, but when I change the parallel core number from 100 to 20, the outcome of the simulation changes a lot. My LAMMPS version is lammps-17Nov16, and my input file is as follows:
variables input
variable DT equal 2.0
variable A equal 220
variable r equal 10
variable L equal 75
variable THERMO equal 5000
variable Pstart equal -0.510$A
variable Pstop equal -0.510$A
init
units real
dimension 3
boundary p p p
atom_style full
timestep ${DT}
neighbor 2.0 bin
neigh_modify delay 0 every 1 check yes
create geometry
pair_style lj/long/tip4p/long long long 2 1 1 1 0.1546 9 8.5
kspace_style pppm/disp/tip4p 1e-5
kspace_modify force/disp/real 0.0001 force/disp/kspace 0.002 mix/disp geom
bond_style harmonic
angle_style harmonic
read_data data.droplet_npt
variables output
variable PRESS equal press
variable VOL equal vol
fixes
fix 0 all indent 10.0 sphere $L $L $L r units box
fix 1 all shake 0.0001 100 0 b 1 a 1
fix barostat all npt temp 298.0 298.0 (100.0*dt) iso {Pstart} {Pstop} (1000.0*dt) drag 1.0
fix print_press all print 1 "{PRESS}" file press.dat screen no title “”
fix print_vol all print 1 “${VOL}” file vol.dat screen no title “”
run
thermo_style custom step temp press vol
thermo ${THERMO}
run 250000
The simulation is designed to mimic the cavitation in water at a low pressure, and the “outcome changes a lot” means the vol-time curves in the simulations are different. The vol variable in the 100 core simulation is increasing much quicker than in the 20 core simulation, which makes me confused.
What I want to ask for advice is that is there any other factors except the “floating point error” that cause this situation? Because I think the the “outcome change” in the two simulation is really beyond my expectation.