fix shakeH all shake 0.0001 20 500 m 1.0079 #H shake
velocity all create 300 12345678 dist uniform
run 0
velocity all scale 300
fix fxnpt2 all npt temp 300.0 300.0 $(100.0*dt) iso 0.98692 0.98692 $(1000.0*dt)
run 5000
unfix fxnpt2
dump 4 all custom 100 traj_nvt.lammpstrj id mol type x y z ix iy iz
fix fxnvt all nvt temp 300.0 300.0 100.0 tchain 1
thermo 100
run 1000
write_data system_after_nvt.data
undump 4
unfix fxnvt