create two solid liquid phase

Hi lammps User,

I want to try two phase coexisting method to calculate the melting
temperature, my code is in below, after running this code, I can not
get two separate phase, also at first of run the average temperature
decreasing too fast and get the value about half of first temperature.
Please help me.

# 3d EAM melt

units metal
atom_style atomic
boundary p p p
lattice fcc 3.52
region box block 0 5 0 5 0 5
#boundary p p p mean all dimensions are PBC
create_box 1 box
#create_box 1 box -> 1 is number of atom types
create_atoms 1 box

group cool id <= 250
group hot id 251 500

mass 1 58.710
velocity all create 500 493389 dist gaussian

pair_style eam
pair_coeff * * Ni_u3.eam

neighbor 0.5 bin
neigh_modify every 5 delay 0 check no

fix fixid1 hot npt temp 500.0 500.0 10 iso 1.0 1.0 100
fix fixid2 cool npt temp 500.0 500.0 10 iso 1.0 1.0 100

dump dumpid all atom 1000 dump.melt
dump_modify dumpid scale no

thermo_style custom step temp press vol pe ke etotal
thermo 200

timestep 0.001
run 100000

unfix fixid1
unfix fixid2

fix fixid2 cool npt temp 1200.0 1200.0 10 iso 1.0 1.0 100
fix fixid1 hot npt temp 3000.0 3000.0 10 iso 1.0 1.0 100
run 500000

Questions like: I want to do something complex,
my script does not work, what is wrong?

will generally not be answered since no one
will spend the time to investigate.

I do notice that you are defining 2 fix npt commands,
which is a bad idea. You shouldn't control
the box size twice.

Steve