[lammps-users] Lithium MEAM


we're trying to use LAMMPS for calculations on Lithium with the default
MEAM library. Unfortunately, the default BCC structure seems unstable even
at very low temperatures (10K). This is evident when looking at the
results with xmovie or by looking at the final radial distribution

Furthermore by doing a volume analysis, it appears the equilibrium lattice
has a lattice size of 3.59 A instead of the 3.50 A indicated in the
library.meam file. Attached is a graph showing the behavior.

The calculation is completed with 1024 atoms over 10000 steps or more
(doing a million steps changes nothing).

See below the input file.
Any suggestions would be greatly appreciated.

Vincent Chevrier

PhD Candidate
Physics Department
Dalhousie University

************************ input file ****************
units metal
boundary p p p

atom_style atomic

lattice bcc 3.50 # Lattice= sc, fcc, bcc, diamond
region box block 0 8 0 8 0 8
create_box 1 box
create_atoms 1 box

pair_style meam
pair_coeff * * library.meam Li NULL Li

neighbor 2.0 bin
neigh_modify delay 1

variable sim_temp equal 10.0

velocity all create \{sim\_temp\} 4928459 rot yes dist gaussian fix 1 all nvt {sim_temp} ${sim_temp} 0.001 drag 0.2
thermo 10
timestep 0.001

dump 1 all atom 10 dump.meam
thermo_style custom step temp press pe ke etotal vol lx ly lz &
xlo xhi ylo yhi zlo zhi pxx pyy pzz pxy pxz pyz
thermo 5

run 10000

write_restart restart.file_equi
*****************end of input file ***********************

a_epot.pdf (14.3 KB)