Dear Steve,
I have some questions about LAMMPS manual.
1. When I learning fix deform command, there is a sentence in manual “For the scale, vel, erate, trate, volume, and wiggle styles, the box length is expanded or compressed around its mid point.” What does this mean? Furthermore, when I using this command for tensile strain simulation, how does it work on the atoms, which part’s postion has changed by this command?
2. Following is shear example from LAMMPS example.
3d metal shear simulation
units metal
boundary s s p
atom_style atomic
lattice fcc 3.52
region box block 0 16.0 0 10.0 0 2.828427
create_box 3 box
lattice fcc 3.52 orient x 1 0 0 orient y 0 1 1 orient z 0 -1 1 &
origin 0.5 0 0
create_atoms 1 box
pair_style eam
pair_coeff * * Ni_u3.eam
neighbor 0.3 bin
neigh_modify delay 5
region lower block INF INF INF 0.9 INF INF
region upper block INF INF 6.1 INF INF INF
group lower region lower
group upper region upper
group boundary union lower upper
group mobile subtract all boundary
set group lower type 2
set group upper type 3
void
#region void cylinder z 8 5 2.5 INF INF
#delete_atoms region void
temp controllers
compute new3d mobile temp
compute new2d mobile temp/partial 0 1 1
equilibrate
velocity mobile create 300.0 5812775 temp new3d
fix 1 all nve
fix 2 boundary setforce 0.0 0.0 0.0
fix 3 mobile temp/rescale 10 300.0 300.0 10.0 1.0
fix_modify 3 temp new3d
thermo 25
thermo_modify temp new3d
timestep 0.001
run 100
shear
velocity upper set 1.0 0 0
velocity mobile ramp vx 0.0 1.0 y 1.4 8.6 sum yes
unfix 3
fix 3 mobile temp/rescale 10 300.0 300.0 10.0 1.0
fix_modify 3 temp new2d
dump 1 all atom 100 dump.shear
thermo 100
thermo_modify temp new2d
reset_timestep 0
run 3000
When I using fix nvt command for thermostatting rather than fix nve and fix temp/rescale command, why can’t it simulate shear deformation? Is there some velocity limitation for using fix nvt command?
Best regards,
M.C.