# [lammps-users] Killed error while calculating melting point for Al

Dear Lammps helpers,

I have been facing a “killed” without any warnings while I was trying to find the Melting point of Al. I faced this problem at temp 900 and 1000 C. I would appreciate assistance with why I get this error. Please find below my input script.

# Calculating the melting point of Al by LAMMPS

# *********************************** Initialization Section ****************************************

units metal
dimension 3
boundary p p p

# *********************************** Creating Atoms ************************************************

atom_style atomic
lattice fcc 4
region box block 0 1 0 1 0 1 units lattice
create_box 1 box
create_atoms 1 box
replicate 6 6 6

# ************************************* Interatomic Potential Settings ******************************

pair_style eam/fs
pair_coeff * * Al1.eam.fs Al

# ************************************* Run Minimization *******************************************

timestep 0.001
thermo 100
velocity all create 900.0 4928459 rot yes dist gaussian
fix 1 all box/relax iso 0.0 vmax 0.001
thermo_style custom step pe lx ly lz press pxx pyy pzz
min_style cg
minimize 1e-25 1e-25 5000 10000
run 1000
unfix 1
write_restart restart.boxmin

# ************************************* Applying temperature ***************************************
fix 2 all npt temp 1000.0 1000.0 100.0 iso 0.0 1.0 100.0
thermo_style custom step atoms temp press vol lx ly lz density time elaplong etotal enthalpy elapsed
dump 1 all xyz 10000 file.*.xyz
run 1000000
write_restart restart.equil

# ************************************* Output Section *********************************************

variable length1 equal "lx/6"
variable length2 equal "ly/6"
variable length3 equal "lz/6"
print "Lattice constant a (Angstoms) = \{length1\};&quot; print &quot;Lattice constant b \(Angstoms\) = {length2};"
print "Lattice constant c (Angstoms) = \${length3};"

Meral

Dear Lammps helpers,

I have been facing a “killed” without any warnings while I was trying to find the Melting point of Al. I faced this problem at temp 900 and 1000 C. I would appreciate assistance with why I get this error. Please find below my input script.

This kind of message is not caused by LAMMPS but must be due to the environment where you are running.
It can for example happen, if you are running in a batch system and your allotted wall time has expired. In that case there should be output files with the corresponding information generated by the batch system. Other than that it can happen when you run interactively on a shared use machine and some calculation (not necessarily yours) exhausts the available memory and the kernel will kill (random) active processes to make room to continue running. This uses heuristics that do their best to identify the cause, but those do not always work.

Please also note that the proper way to determine the melting point of a solid are coexistence simulations. This has been discussed in the past multiple times, so I suggest you dig into the mailing list archives and search for those discussions.

Axel.

Applying such a high temperature all of sudden might give trouble in some cases due to shock waves or lost atoms. Plus, as far as I've seen, this code wouldn't allow you to measure the melting point of Al. I suggest you trying with a fix npt applying an initial temperature of, let's say, 300 ºC, a final temperature of 1000 ºC, and store the volume and the temperature of the system every hundred steps, then do a plot of Vol vs T. Don't expect to find that your system melts at the theoretical melting point of Al, and also consider increasing the size of the box.

Álvaro