In the following script, I want to relax to zero pressure in x, y and z directions at a temperture of 300K for 50000 time steps. However, I discovered that the z coordinate of graphene sheet does not change when I commented the line of ‘velocity all create ${T} 4928459 dist gaussian units box’. Can someone explain it to me, thanks.
---------- Variable list ----------
variable steps1 equal 50000 # steps for equilibration
variable T equal 300 # strain rate in x direction
---------- Initialization ----------
units metal
dimension 3
boundary p p p
atom_style atomic
---------- System definition ----------
region box block -12 78 -12 78 -12 12 units box
create_box 1 box
lattice custom 2.4768 &
a1 1.0 0.000 0.0000 &
a2 0.0 1.732 0.0000 &
a3 0.0 0.000 1.3727 &
basis 0.0 0.33333 0.0 &
basis 0.0 0.66667 0.0 &
basis 0.5 0.16667 0.0 &
basis 0.5 0.83333 0.0
region graphene block -12 78 -12 78 -0.5 0.5 units box
create_atoms 1 region graphene
mass 1 12.0
---------- Simulation settings for equilibration -----------
force field
pair_style airebo 2.0
pair_coeff * * CH.airebo C
simulation parameters
neighbor 0.3 bin
neigh_modify delay 0 every 1 check yes
Minimization
min_style cg
minimize 1e-10 1e-10 5000 5000
reset_timestep 0
fixes
timestep 0.0005
velocity all create ${T} 4928459 dist gaussian units box
fix 1 all npt temp T{T} (100∗dt)x00(1000dt) y 0 0 (1000∗dt)z00(1000dt)
computations
Output
thermo 100
thermo_style custom step temp pe etotal press pxx pyy pzz
dump 1 all custom 1000 relaxtiontest.lammpstrj id type x y z
---------- Run simulation for equilibration ----------
run ${steps1}
unfix 1
undump 1
reset_timestep 0
write_data relaxed_test.data
print “All done”