Hi all ,i’m a newbie in lammps.
Here is my simulation script.
Are you running the current, full patched version of LAMMPS?
A couple of bug fixes related to problems of this kind
have been patched since the 9Jan09 release.
Steve
See the script below. If you run with fix_modify commented
out then the potential eng from one run to the next
is identical. If you run with fix_modify it's not. This
is b/c those commands tell LAMMPS to add a energy term
calculated by the NPT fix to the total pot eng. It is a quantity
that takes into account the time history of the Nose/Hoover
integrator. If you unfix the fix, you wipe out the time
history. Thus when you use the new value from the 2nd
npt fix, it will be different.
Steve
# 3d Lennard-Jones melt
units lj
atom_style atomic
lattice fcc 0.8442
region box block 0 10 0 10 0 10
create_box 1 box
create_atoms 1 box
mass 1 1.0
velocity all create 1.0 87287 loop geom
pair_style lj/cut 2.5
pair_coeff 1 1 1.0 1.0 2.5
neighbor 0.3 bin
neigh_modify delay 0 every 20 check no
thermo_style custom step temp pe ke etotal press vol
thermo 20
fix solidify all npt 1.0 0.5 0.5 xyz 1.0 1.0 1.0
#fix_modify solidify energy yes
run 100
unfix solidify
fix equil all npt 0.5 0.5 0.5 xyz 1.0 1.0 1.0
#fix_modify equil energy yes
run 200