Dear Lammps -Users
I have gotten a problem in relaxation of nano-crystalline structure. the structure was first relaxed using a min_style cg with an energy and force tolerance of 1e-7 EV. then the samples were annealed from 300 to 900 k to relax the grain boundaries and then cooled from 900 to 300 K with NPT ensemble, but when i take a look at the dump file , the initial structure was fully 100% bcc structure but after the relaxiation, just 10 were bcc and 90 were other structure (Amorph structure),
I dont know what causes the change in structure, i mean instead of atoms oscillation, the atoms have been moved, here is my input script and the log file,
by the way, i have studied published papers in this field( nanocrystallline) and unfortunately i couldnt apply their simulation methods in my system.
High temperature equilibration (900 K)
units metal
boundary p p p
atom_style atomic
read_data data.FeC
pair_style meam
pair_coeff * * FeC.library.meam Fe C FeC.meam Fe C
neighbor 2.0 bin
neigh_modify delay 10
compute new all temp
compute centro all centro/atom bcc
compute pea all pe/atom
velocity all create 300.0 5812775 temp new
thermo 500
thermo_style custom step temp pe ke etotal press vol lx ly lz pxx pyy pzz pxy pxz pyz
thermo_modify lost warn norm yes temp new
fix 1 all box/relax aniso 0.0 vmax 0.1
timestep 0.0001
min_style cg
min_modify dmax 0.2 line quadratic
minimize 1.0e-7 1.0e-7 1000 1000
dump 1 all cfg 500 dump.1.*.cfg mass type xs ys zs vx vy vz
dump_modify 1 element Fe C
unfix 1
fix 1 all npt temp 300.0 900.0 0.1 iso 0.0 0.0 1000.0
fix 2 all temp/rescale 10 300.0 900.0 10.0 1.0
fix_modify 2 temp new
dump 2 all cfg 500 dump.1.*.cfg mass type xs ys zs vx vy vz
dump_modify 2 element Fe C
log log1.data
run 3000
unfix 1
unfix 2
fix 1 all npt temp 900.0 300.0 100 iso 0.0 0.0 1000.0
fix 2 all temp/rescale 10 900.0 300.0 10.0 1.0
fix_modify 2 temp new
dump 3 all cfg 500 dump.3.*.cfg mass type xs ys zs vx vy vz
dump_modify 3 element Fe C
log log2.data
restart 1000 relax.restart
run 10000
Log file:
LAMMPS (24 Dec 2015)
High temperature equilibration (900 K)
units metal
boundary p p p
atom_style atomic
read_data data.FeC
orthogonal box = (0 0 0) to (140 100 80)
2 by 2 by 1 MPI processor grid
reading atoms …
88876 atoms
pair_style meam
pair_coeff * * FeC.library.meam Fe C FeN.meam Fe C
neighbor 2.0 bin
neigh_modify delay 10
compute new all temp
compute centro all centro/atom bcc
compute pea all pe/atom
velocity all create 300.0 5812775 temp new
thermo 500
thermo_style custom step temp pe ke etotal press vol lx ly lz pxx pyy pzz pxy pxz pyz
thermo_modify lost warn norm yes temp new
fix 1 all box/relax aniso 0.0 vmax 0.1
timestep 0.0001
min_style cg
min_modify dmax 0.2 line quadratic
minimize 1.0e-7 1.0e-7 1000 1000
WARNING: Resetting reneighboring criteria during minimization (…/min.cpp:168)
Neighbor list info …
3 neighbor list requests
update every 1 steps, delay 0 steps, check yes
max neighbors/atom: 2000, page size: 100000
master list distance cutoff = 6
ghost atom cutoff = 6
binsize = 3 -> bins = 47 34 27
Memory usage per processor = 42.8212 Mbytes
Step Temp PotEng KinEng TotEng Press Volume Lx Ly Lz Pxx Pyy Pzz Pxy Pxz Pyz
0 300 -4.1405444 0.038777607 -4.1017668 -6558.6124 1120000 140 100 80 -6616.8224 -6820.6017 -6238.4129 -54.283977 609.05672 240.92253
33 300 -4.1605599 0.038777607 -4.1217823 530.58275 1114851.1 139.90798 99.822006 79.826684 -1449.7818 1347.6099 1693.9201 -40.160126 929.12402 19.99202
Loop time of 56.2653 on 4 procs for 33 steps with 88876 atoms
96.3% CPU use with 4 MPI tasks x no OpenMP threads
Minimization stats:
Stopping criterion = energy tolerance
Energy initial, next-to-last, final =
-4.1405444382 -4.16055956552 -4.16055986758
Force two-norm initial, final = 11928.5 3799.99
Force max component initial, final = 7067.09 3302.27
Final line search alpha, max atom move = 3.20355e-05 0.10579
Iterations, force evaluations = 33 85
MPI task timing breakdown:
Section | min time | avg time | max time |%varavg| %total