Dear all,
I am trying to do NVT simulation of Cu64Zr36 alloy using EAM potential. Following is the input script file
units metal
boundary p p p
atom_style atomic
read_data datacuzr.eam
mass 1 63.546
mass 2 91.224
velocity all create 2200.0 49284598 rot yes dist gaussian
pair_style eam/alloy
pair_coeff * * Cu-Zr.eam.fs Cu Zr
neighbor 2.0 bin
neigh_modify delay 50
run_style verlet
fix 1 all nvt 2200.0 2200.0 100.0 drag 0.2
thermo_style custom step temp pe etotal press vol
thermo 500
timestep 0.001
dump mydump all custom 1000 dump.eam tag type x y z vx vy vz
run 20000
When the delay is kept 50 in neigh_modify command, the atoms are lost immediately after the first run. When the delay is kept 5 & thermo command is modified to give output at 1 step the following is the result:
LAMMPS (21 May 2008)
Reading data file …
orthogonal box = (-15.2855 -15.2855 -15.2855) to (15.2855 15.2855 15.2855)
1 by 1 by 1 processor grid
1000 atoms
Setting up run …
Memory usage per processor = 1.87976 Mbytes
Step Temp PotEng TotEng Press Volume
0 1469.6005 -6.1940187e+12 -6.1940187e+12 -2.5327465e+17 28571.429
1 6.4441288e+26 27632.791 8.3213605e+25 3.1108673e+27 28571.429
2 0 27632.791 27632.791 0 28571.429
3 0 27632.791 27632.791 0 28571.429
4 0 27632.791 27632.791 0 28571.429
ERROR: Lost atoms: original 1000 current 0
It can be observed that there is something wrong immediately after first run. By trial & error, I found that when the timestep is set to 1e-19 & thermo command is modified to give output at every 500 steps, the following is the result
LAMMPS (21 May 2008)
Reading data file …
orthogonal box = (-15.2855 -15.2855 -15.2855) to (15.2855 15.2855 15.2855)
1 by 1 by 1 processor grid
1000 atoms
Setting up run …
Memory usage per processor = 1.87976 Mbytes
Step Temp PotEng TotEng Press Volume
0 1469.6005 -6.1940187e+12 -6.1940187e+12 -2.5327465e+17 28571.429
500 1476.4914 -6.1940187e+12 -6.1940187e+12 -2.5327465e+17 28571.429
1000 1496.2707 -6.1940187e+12 -6.1940187e+12 -2.5327465e+17 28571.429
1500 1528.9381 -6.1940187e+12 -6.1940187e+12 -2.5327465e+17 28571.429
2000 1574.4939 -6.1940187e+12 -6.1940187e+12 -2.5327465e+17 28571.429
2500 1632.9378 -6.1940187e+12 -6.1940187e+12 -2.5327465e+17 28571.429
3000 1704.2701 -6.1940187e+12 -6.1940187e+12 -2.5327465e+17 28571.429
3500 1788.4906 -6.1940187e+12 -6.1940187e+12 -2.5327465e+17 28571.429
4000 1885.5994 -6.1940187e+12 -6.1940187e+12 -2.5327465e+17 28571.429
4500 1995.5964 -6.1940187e+12 -6.1940187e+12 -2.5327465e+17 28571.429
5000 2118.4816 -6.1940187e+12 -6.1940187e+12 -2.5327465e+17 28571.429
5500 2254.2552 -6.1940187e+12 -6.1940187e+12 -2.5327465e+17 28571.429
6000 2402.917 -6.1940187e+12 -6.1940187e+12 -2.5327465e+17 28571.429
6500 2564.467 -6.1940187e+12 -6.1940187e+12 -2.5327465e+17 28571.429
7000 2738.9053 -6.1940187e+12 -6.1940187e+12 -2.5327465e+17 28571.429
7500 2926.2319 -6.1940187e+12 -6.1940187e+12 -2.5327465e+17 28571.429
… …
It can be observed that the temperature continuously increases. For large number of runs, it increases beyond the target temperature.
I do not understand what is going wrong.
Please let me know what should I do.
Kirit Lad
Lecturer
Applied Physics Department
Faculty of Technology & Engineering
The Maharaja Sayajirao University of Baroda
Vadodara-390001, Gujarat, INDIA |
Dear Kirit,
There’s something wrong with your initial configuration. Look how small your pressure is at step 0 (-2.5327465e+17). Look how large your temperature is at step 1 (6.4441288e+26). You should check for overlapping atoms in the input configuration.
Joanne