Greetings everyone!
I’m simulating the melting process of small sodium clusters, typically of 189 or 341 atoms. For some reason the melting begins at 50 or 70 K temperatures whereas experiments give 260 K melting point for sodium clusters of the same size. The physics of the process itself is OK and all I need to fix is this odd shift of melting temperature. Could you give me any suggestions where is the problem could lie?
I used eam.fs potential from NIST repository. There is my LAMMPS code:
Sodium melting
units metal
boundary f f f
atom_style atomic
lattice bcc 4.23
region my_lattice block 0 5 0 5 0 5
region outside block -12 18 -12 18 -12 18
region box intersect 2 my_lattice outside
create_box 1 outside
create_atoms 1 region my_lattice
pair_style eam/fs
pair_coeff * * /usr/share/lammps/potentials/Na.eam.fs Na
thermo 1
timestep 0.001
neighbor 0.3 bin
neigh_modify every 1 delay 0
------ relax the cluster
minimize 1.e-10 1.e-10 1000 100000
reset_timestep 0
velocity all create 10 123465 mom yes rot yes dist gaussian
fix 1 all nvt temp 10 210 0.1
compute vol all voronoi/atom
thermo 10
thermo_style custom step temp
dump 1 all custom 20 Na_3.lammpstrj id type x y z c_vol[1]
write_data data.Na_3
thermo_style custom step temp
run 100000
Regards,
Grad student
SPBU
Ruslan Mukhamadiarov