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lammps/examples/friction/in.friction
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in.friction
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# 2d friction simulation
dimension 2
boundary p s p
atom_style atomic
neighbor 0.3 bin
neigh_modify delay 5
# create geometry
lattice hex 0.9
region box block 0 50 0 22 -0.25 0.25
create_box 4 box
mass 1 1.0
mass 2 1.0
mass 3 1.0
mass 4 1.0
# atom regions
region lo-fixed block INF INF INF 1.1 INF INF
region lo-slab block INF INF INF 7 INF INF
region above-lo block INF INF INF 7 INF INF side out
region hi-fixed block INF INF 20.9 INF INF INF
region hi-slab block INF INF 15 INF INF INF
region below-hi block INF INF 15 INF INF INF side out
region lo-asperity sphere 32 7 0 8
region hi-asperity sphere 18 15 0 8
region lo-half-sphere intersect 2 lo-asperity above-lo
region hi-half-sphere intersect 2 hi-asperity below-hi
# create 2 surfaces with asperities
create_atoms 1 region lo-slab
create_atoms 1 region hi-slab
create_atoms 2 region lo-half-sphere
create_atoms 3 region hi-half-sphere
# LJ potentials
pair_style lj/cut 2.5
pair_coeff * * 1.0 1.0 2.5
# define groups
group lo region lo-slab
group lo type 2
group hi region hi-slab
group hi type 3
group lo-fixed region lo-fixed
group hi-fixed region hi-fixed
group boundary union lo-fixed hi-fixed
group mobile subtract all boundary
set group lo-fixed type 4
set group hi-fixed type 4
# initial velocities
compute new mobile temp/partial 0 1 0
velocity mobile create 0.1 482748 temp new
velocity hi set 1.0 0.0 0.0 sum yes
# fixes
fix 1 all nve
fix 2 boundary setforce 0.0 0.0 0.0
fix 3 mobile temp/rescale 200 0.1 0.1 0.02 1.0 partial 0 1 0
# Run
timestep 0.0025
thermo 1000
thermo_modify temp new
dump 1 all atom 500 dump.friction
run 20000
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