Hi,

I wish to simulate Argon using LJ potential in order to determine its melting transition temperature. From the literature, the melting temperature for Argon is 83.8K. After the simulation, I plotted a graph of volume vs temperature from the output. Unfortunately, I see no abrupt change in the volume at temperature ~83K. Is there any mistake in my input file? Thank you.

# LAMMPS melt_argon

units real

boundary p p p

atom_style atomic

dimension 3

lattice fcc 5.260

region box block 0 10 0 10 0 10

create_box 1 box

create_atoms 1 box

pair_style lj/cut 3.5

pair_coeff 1 1 0.238067 3.405

group Ar type 1

mass 1 39.948

timestep 0.001

thermo 1000

neighbor 0.6 bin

neigh_modify every 1 delay 0 check no

variable N equal step

variable pote equal pe

variable Etotal equal etotal

variable T equal temp

variable Press equal press

variable V equal vol

variable kine equal ke

compute 3 all pe/atom

compute 4 all ke/atom

compute 5 all coord/atom 3.0

compute 6 all temp

velocity all create 0.01 112387 dist gaussian

fix extra all print 100 “{N} {T} {V} {Press} {kine} {pote} ${Etotal}” file data

fix 1 all nvt temp 0.01 0.01 1.0 drag 0.2

run 20000

unfix 1

fix 1 all npt temp 0.01 300.0 10.0 iso 1.0 1.0 1.0

run 500000