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[lammps-users] NANOMACHINING


From: "Abdulkadir, Lukman, (Mr) (s215102134)" <s215102134@...6642...>
Date: Tue, 4 Jul 2017 16:38:23 +0000

Hello all,
I need some help with my MD simulation. I am working on MD simulation of nanomachining of silicon, my script is as written bellow:

# in.Si_C
dimension 3
units metal
#newton on
boundary p p p
atom_style atomic
pair_style tersoff

read_data   data.finalSi_C2change

pair_coeff * * SiC.tersoff Si Si Si C

#pair_coeff 1 * eam Cu_u3.eam
#pair_coeff 3 * eam Cu_u3.eam
#pair_coeff 4 4 eam Cu_u3.eam

#pair_coeff 1 2 lj/cut 0.4096 2.338
#pair_coeff 2 3 lj/cut 0.4096 2.338
#pair_coeff 2 4 lj/cut 0.4096 2.338

neighbor 2.0 bin
neigh_modify delay 2
neigh_modify exclude type 4 4

group newtonian type 1
group thermostat type 2
group boundary type 3
group tool type 4
group mobile subtract all boundary tool

fix 1 tool rigid single

#fix 1 thermostat rigid single

# initial velocities

compute new mobile temp
velocity mobile create 293 564329 temp new
velocity tool set 2.0 0 0 sum yes units box

fix 2 mobile nve

#fix 2 all nve

#unfix 2

fix 3 mobile temp/rescale 10 293 293 0.01 1.0
fix_modify 3 temp new
fix 4 boundary setforce 0.0 0.0 0.0
fix 5 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
thermo_modify lost warn
compute_modify new extra 3
dump 1 all atom 500 dump.Si_C
dump_modify 1 scale no
dump 2 all custom 1000 dump.forceSi_C.* id type x y z vx vy vz fx fy fz
timestep 0.0003
run 100000

If i remove the comment on "unfix 2" my mobile atoms remained in the box but the tool just passed and the atoms joined again FIGURE 1 (as if my tool is embedded in the workpiece) and the workpiece is not machined. But when i put comment on "unfix 2" (i.e. #unfix 2) the atoms expands and bulge even before the approach of the tool (FIGURE 2). I need the tool to displace (machine) the workpiece as shown in FIGURE 3. I am using LAMMPS version 20170127


Can anybody please help? 
The figures are attached.

Attachment: FOR LAMMPS MAILING LIST 2.pdf
Description: FOR LAMMPS MAILING LIST 2.pdf