The simulation of pure iron-titanium metal connection, with iron on top and titanium below. The top and bottom three layers of atoms are fixed, the NVT ensemble relaxation is performed, and then compression is carried out using the fix move command. The compression is divided into two stages; the first stage is fast, and after compressing to a certain extent, the second stage of compression is performed at a slower speed. The current issue is why there is almost no diffusion during the compression process. Below are my code and simulation results.
#Basic model settings
units metal
atom_style atomic
boundary p p p
timestep 0.001
neighbor 2 bin
neigh_modify every 1 delay 0
#ModelingEstablishment
region box block 0 40 0 40 0 100 units box
create_box 2 box
lattice bcc 2.86
region Fe block 0 14 0 14 20 34 units lattice
create_atoms 1 region Fe
lattice custom 2.92 a1 1.0 0.0 0.0 a2 0.0 1.732 0.0 a3 0.0 0.0 1.633 &
basis 0.0 0.0 0.0 &
basis 0.5 0.5 0.0 &
basis 0.5 0.83333 0.5 &
basis 0.0 0.33333 0.5
region Ti block 0 14 0 8 0 9 units lattice
create_atoms 2 region Ti
region upper block INF INF INF INF 93 INF units box
region lower block INF INF INF INF INF 5 units box
#Potential function
pair_style meam
pair_coeff * * library.meam Fe Ti FeTi.meam Fe Ti
#Grouping
group Fe type 1
group Ti type 2
group upper region upper
group lower region lower
group boundary union upper lower
group chiyu subtract all boundary
group Fechiyu subtract Fe upper
group Tichiyu subtract Ti lower
#FixedAtom
velocity upper set 0 0 0 units box
velocity lower set 0 0 0 units box
fix 1 boundary setforce 0 0 0
energy Minimization
minimize 1e-10 1e-12 10000 10000
write_data zuixiaohua.data
#Temperature Initialization
velocity Fechiyu create 1173 12345
velocity Tichiyu create 1173 12345
#Relaxation
fix 222 Fechiyu nvt temp 1173 1173 0.1
fix 333 Tichiyu nvt temp 1173 1173 0.1
thermo 1000
thermo_style custom step temp press pzz pe ke etotal
dump 1 all xyz 1000 cy1.xyz
run 200000
unfix 222
unfix 333
undump 1
Motion Control
reset_timestep 0
fix 6 upper move linear 0 0 -0.06 units box
fix 7 Fechiyu nvt temp 1173 1173 0.1
fix 8 Tichiyu nvt temp 1173 1173 0.1
variable pzz1 equal pzz
variable step1 equal step
fix 9 all ave/time 100 5 1000 v_step1 v_pzz1 file stress2.txt
thermo_style custom step temp press pzz pe ke etotal
dump 3 all custom 1000 kuai.xyz id type x y z
run 150000
unfix 6
unfix 7
unfix 8
unfix 9
undump 3
Motion Control
reset_timestep 0
fix 10 upper move linear 0 0 -0.0006 units box
fix 11 Fechiyu nve
fix 12 Tichiyu nve
variable pzz2 equal pzz
variable step2 equal step
fix 13 all ave/time 100 5 1000 v_step2 v_pzz2 file stress2.txt
thermo_style custom step temp press pzz pe ke etotal
dump 4 all custom 1000 man.xyz id type x y z
run 500000
The following are the results after running 500,000 steps, and it can be seen that the atoms have hardly diffused. What could be the reason?
