We tried to reproduce some calculations on liquid nickel performed by Cherne et al. (PRB 65 (2001) 24209) with an MEAM potential. They studied the melting of a bulk Ni sample at 1726K by using the Ni4 potential published by Baskes.
The melting temperature reported by Cherne et al. is 1570K. We used the same system : 1372 atoms, NPT relaxation followed by NVE runas. However, even at 1775K we were not able to observe the melting of the sample.
We also tried to study the self diffusion of Ni in a bulk which contains several vacancies at high temperature. We did not observe any diffusion !!! So I'm wondering if someone already find the same kind of problem with LAMMPS and the MEAM potential.
We have been trying to solve this for a long time, any suggestion is highly appreciated!
Note that, We used the following files :
==> library.meam provided with LAMMPS. We replaced in this file the initial value of ibar for Ni4 by 3 to agree with Baskes (Mat. Chem. Phys. 50 (1997) 152).
re(1,1) = 2.49
Cmin(1,1,1) = 0.8
rc = 4.0
delr = 0.1
boundary p p p
lattice fcc 3.52
region box block 0 7.0 0 7.0 0 7.0
create_box 1 box
create_atoms 1 box
pair_coeff * * ./library.meam Ni4 ./Ni.meam Ni4
neighbor 0.3 bin
neigh_modify delay 10
thermo_style custom step temp ke pe etotal lx ly lz vol press
compute Temperature all temp
velocity all create 1775.0 87287
fix 1 all npt 1775.0 1775.0 10.0 aniso 0.0 0.0 0.0 0.0 0.0 0.0 5.0 drag 2.0
fix 3 all temp/rescale 1 1775.0 1775.0 10.0 1.0
compute 4 all ackland/atom
compute 6 all centro/atom
dump 2 all custom 5000 Ni-npt.xyz tag x y z type c_4 c_6
dump 2 all custom 10000 Ni-nve.xyz tag x y z type c_4 c_6
fix msdni all msd 500 msd-ni.out
fix 1 all nve