[lammps-users] Morse potential

Hello everyone,

I have a problem when I run the example of in.iondent under the directory of lammps. I only change the LJ potentials to the Morse potential parameters. But the object was expanded and tha atoms arranged disorderly The morse parameters is the single Cu. I also found the same problems when I run the other problems using the Morse potential parameters. Yet It havn’t this problem when I use the other potential parameters. Why?

Many thanks,
Liu Jun

This is the in.indent that I use.

2d indenter simulation

dimension 2
boundary p s p
atom_style atomic
neighbor 0.3 bin
neigh_modify delay 5

create geometry

lattice hex 0.9
region box block 0 20 0 10 -025 0.25
create_box 2 box
create_atoms 1 box
mass 1 1.0
mass 2 1.0

LJ potentials were changed

pair_style morse 2.5
pair_coeff * * morse 0.3429 1.3588 2.875

define groups

region 1 block INF INF INF 1.25 INF INF
group lower region 1
group mobile subtract all lower
set group lower type 2

initial velocities

compute new mobile temp
velocity mobile create 0.2 482748 temp new
fix 1 all nve
fix 2 lower setforce 0.0 0.0 0.0
fix 3 all temp/rescale 100 0.1 0.1 0.01 1.0

indenter

fix 4 all indent 1000.0 sphere 10 13 0 5.0 vel 0.0 -0.02 0.0
fix 5 all enforce2d

Run with indenter

timestep 0.003
thermo 1000
thermo_modify temp new
dump 1 all atom 250 dump.indent
run 30000

Run without indenter

unfix 4
run 30000

Check the units you're using. The in.indent example is
in LJ units. Is your Morse potential parameterized for LJ
or some other units?

Steve

2008/2/24 hmpen23 <[email protected]>: