Hello everyone!
I try to perform a “lateral pressure simulation test” to measure v21 of carbon nanotubes (CNTs). I found in the the mail list that " if that pressure is positive, it will try to compress the system, if it is negative, it will expand the system. since the pressure at inifinite dilution is zero, a negative external pressure will always expand your system. " “thus you can have a balance between internal and external pressure only for positive pressure values.”
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so I can not balance the system in Negative pressure and make CNTs enlarge (with command
fix 1 all npt temp 4.3 4.3 1 y 0 0 1 x -5 -5 5 z -5 -5 5 couple xz) Am I right? -
then if i set a positive pressure value, box will shrink and finally CNTs turn into the shape of a square due to periodic boundary conditions.
Now i have no idea how to simulate that. Any comments will be highly appreciated. Thanks a lot!
units metal
dimension 3
boundary s p s
atom_style atomic
neighbor 2.0 nsq
neigh_modify every 1 delay 0 check yes
read_data CNt_sortY25-0_103.xyz
pair_style airebo 3.0 1 1
pair_coeff * * CH.airebo C
reset_timestep 0
timestep 0.0005
min_style cg
minimize 1.0e-6 1.0e-6 10000 1000
change_box all boundary p p p
change_box all z delta -10 10 units box
change_box all x delta -10 10 units box
velocity all create 4.3 4928459 dist gaussian mom yes rot yes
reset_timestep 0
fix 1 all npt temp 4.3 4.3 0.1 y 0 0 1 x 0 0 1 z 0 0 1 couple xz
dump 1 all custom 20 relaxation-deform.dat id type x y z
run 200000
unfix 1
undump 1
# ------------------------ DEFORMATION--------------------------------------
fix 2 all npt temp 4.3 4.3 1 y 0 0 1 x 0 -5 5 z 0 -5 5 couple xz
run 200000
unfix 2
fix 2 all npt temp 4.3 4.3 1 y 0 0 1 x -5 -10 5 z -5 -10 5 couple xz
run 200000
unfix 2
fix 2 all npt temp 4.3 4.3 1 y 0 0 1 x -10 -15 5 z -10 -15 5 couple xz
run 200000
unfix 2
fix 2 all npt temp 4.3 4.3 1 y 0 0 1 x -15 -20 5 z -15 -20 5 couple xz
run 400000
unfix 2
fix 2 all npt temp 4.3 4.3 1 y 0 0 1 x -20 -25 5 z -20 -25 5 couple xz
run 600000
unfix 2
fix 2 all npt temp 4.3 4.3 1 y 0 0 1 x -25 -30 5 z -25 -30 5 couple xz
run 800000
unfix 2
print "All done"