[lammps-users] On MEAM Potential for Copper and Cabon atoms

Hi all,

l am trying to use the MEAM potential to model both copper and carbon atoms.

I have 4 atom types.

The simulation ran for 7000 steps and then, l started to get results like - ‘nan’.

What could be wrong and what does ‘nan’ mean?

Please, see below.

Thanks.

Jide

LAMMPS (12 Oct 2010)

in.cu_C

units metal
boundary f f s
atom_style atomic
pair_style meam

read_data data.cu_C

pair_coeff * * library.meam Cu C NULL Cu C Cu Cu

neighbor 3.0 bin
neigh_modify delay 3
#neigh_modify exclude type 1 1

initial velocities

compute new mobile temp
velocity mobile create 293 564329 temp new
velocity tool set 1.5 0 0 sum yes units box
fix 1 all nve
fix 2 mobile temp/rescale 1.0 293 293 10.0 1.0
fix_modify 2 temp new
fix 3 boundary setforce 0.0 0.0 0.0
fix 4 tool setforce 0.0 0.0 0.0
velocity thermostat scale 293.0

thermo 500
thermo_style custom step temp epair pe ke etotal vol press
thermo_modify temp new
WARNING: Temperature for thermo pressure is not for group all
thermo_modify lost warn
compute_modify new extra 4
dump 1 all atom 500 dump.cu_C
dump_modify 1 scale no
dump 2 all custom 1000 dump.forcecu_C.* id type x y z vx vy vz fx fy fz
timestep 0.0003
run 100000

Step Temp E_pair PotEng KinEng TotEng Volume Press
0 292.81172 -185028.81 -185028.81 1358.9516 -183669.86 19947895 10199.423
500 296.30526 -184592.95 -184592.95 1375.1653 -183217.79 19947895 10162.361
1000 296.99952 -184549.71 -184549.71 1378.3874 -183171.32 19947895 10148.014
1500 294.44005 -184537.83 -184537.83 1366.5087 -183171.32 19947895 10139.382
2000 295.814 -184544.21 -184544.21 1372.8853 -183171.32 19947895 10118.9
2500 296.57056 -184547.72 -184547.72 1376.3966 -183171.32 19947895 10108.154
3000 294.94164 -184540.16 -184540.16 1368.8366 -183171.32 19947895 10095.009
3500 294.36942 -184537.5 -184537.5 1366.1809 -183171.32 19947895 10084.798
4000 296.89624 -184549.23 -184549.23 1377.908 -183171.32 19947895 10076.112
4500 293.65764 -184534.2 -184534.2 1362.8775 -183171.32 19947895 10070.865
5000 295.46777 -184542.6 -184542.6 1371.2784 -183171.32 19947895 10063.762
5500 295.31715 -184541.9 -184541.9 1370.5794 -183171.32 19947895 10066.424
6000 295.26177 -184541.64 -184541.64 1370.3224 -183171.32 19947895 10066.552
6500 295.41037 -184542.33 -184542.33 1371.0121 -183171.32 19947895 10072.391
7000 294.70993 -184539.08 -184539.08 1367.7613 -183171.32 19947895 10075.935
7500 nan nan nan nan nan 19947895 nan
8000 nan nan nan nan nan 19947895 nan

Something in your simulation blew up. I would print
out thermo info more frequently, like every step.

Steve