Dear lammps user
Hello
I want to simulate nanoindentation on single crystal nickel.
I create a simulation box = (0 0 -20 ) to (180 180 220) and deleted atoms upper side and bottom side for forming free surface.
---------------------------- INITIALLIZE ----------------------------
units metal
dimension 3
boundary p p p
atom_style atomic
-------------------------- ATOM DEFINITION --------------------------
lattice fcc 3.52
region sample block 0 180 0 180 -20 220 units box
create_box 1 sample
create_atoms 1 region sample
mass 1 58.6934
---------------------------- FORCE FIELD ---------------------------
pair_style eam
pair_coeff * * Ni_u3.eam
------------------------ Making free surface -----------------------
region up block INF INF INF INF 150 INF units box
group slap1 region up
delete_atoms group slap1
region down block INF INF INF INF INF 0 units box
group slap2 region down
delete_atoms group slap2
------------------- Calculate/Extract energy of each atom -------------------
compute csym all centro/atom fcc
compute eng all pe/atom
compute eatoms all reduce sum c_eng
thermo 50
thermo_style custom step temp pe ke press pxx pyy pzz lx ly lz
thermo_modify norm no
---------------------- Setting ensemble (NVE) ----------------------
fix 1 all nve
Before indentation test, I do minimize the structure by using below scripts.
-------------------- Minimization/Stress relaxation --------------------
dump 2 all custom 500 dump.initialnickel id type xs ys zs c_csym c_eng fx fy fz
min_style cg
minimize 1e-10 1e-12 10000 100000
run 10000
velocity all create 300.0 4928459
fix 3 all temp/rescale 10 300.0 300.0 0.01 1.0
min_style cg
minimize 1e-10 1e-12 10000 100000
run 350000
region fixed block INF INF INF INF INF 30 units box
group bottom region fixed
fix 4 bottom setforce 0.0 0.0 0.0 region fixed
From the log file, I knew that the pressure decrease from 825276.87 to 4567.8092 at 0K and stabilized.
And after increasing temperature up to 300 K, pressure increase again to ~16800 and it is fluctuated for a long time step and finally stabilized.
When I check the dump file, however, there are so many dislocations in the Ni structure at both 0 K and 300 K.
(different points at between two temperature: at 0K it is possible to simulate indentation test although there are so many dislocations. But at 300K, LAMMPS show the warning message, which is that ¡°WARNING: Building an occasional neighbor list when atoms may have moved too far (…/neighbor.cpp:1401)¡±, every 200 time step and finally simulation failed with error like ¡°ERROR: Lost atoms: original 450882 current 450880 (…/thermo.cpp:389)¡±)
timestep 0.001
reset_timestep 0
variable b equal “155.0+stepdt0.1”
fix 6 all indent 10.0 sphere 90.0 90.0 v_b 20.0 units box
fix 8 all ave/time 2 5 10 v_a f_6 f_6[1] f_6[2] f_6[3] file PhcurveNi2_unload.indentation
run 155000
I cannot fix this problem. How can I fix it? I appreciate if you can help me solving this problem.
Thanks in advanced.