# sample LAMMPS input script for viscosity of 2d LJ liquid # use shearing wall, thermostat via fix langevin # settings variable x equal 20 variable y equal 20 variable ylo equal -2.5 variable yhi equal 23 variable rho equal 0.6 variable t equal 1.0 variable rc equal 2.5 variable srate equal 2.7 # problem setup units lj dimension 2 atom_style atomic neigh_modify delay 0 every 1 lattice sq2 ${rho} region simbox block 0 $x ${ylo} ${yhi} -0.1 0.1 create_box 3 simbox create_atoms 1 box mass * 1.0 pair_style lj/cut ${rc} pair_coeff * * 1 1 region lower block INF INF INF 0.0 INF INF region upper block INF INF $y INF INF INF group lower region lower group upper region upper set group lower type 2 set group upper type 3 group wall union lower upper group flow subtract all wall velocity flow create $t 97287 velocity upper set ${srate} 0.0 0.0 units box compute thermal flow temp/partial 0 1 0 compute flow flow temp fix 1 all nve fix 2 flow langevin $t $t 0.1 498094 fix_modify 2 temp thermal fix 3 wall setforce 0.0 0.0 0.0 fix 4 flow ave/spatial 20 500 10000 y center 0.05 vx & units reduced file profile.wall.2d fix 5 all enforce2d # equilibration run variable ybox equal $y*ylat compute tilt flow temp/ramp vx 0 ${srate} y 0 ${ybox} units box thermo 1000 thermo_style custom step temp c_tilt epair etotal press pxy run 20000 # data gathering run variable visc equal -pxy/(v_srate/ly) fix vave all ave/time 1000 1 1000 v_visc ave running thermo_style custom step temp pxy v_visc f_vave thermo_modify temp tilt # only need to run for 5000 steps to make a good 100-frame movie #dump 1 all custom 50 dump.wall.2d id type x y z vx #dump 1 all image 50 image.*.jpg vx type zoom 1.6 adiam 1.2 #dump_modify 1 pad 5 amap 0.0 ${srate} ca 0.0 2 min blue max red run 50000