ERROR: Illegal set command (../set.cpp:517)

Dear Sir

I am a new user of LAMMPS. I am trying to simulate for primary radiation damage. Below I have my input script. I am getting the below error

set group PKA vx 109.5108
ERROR: Illegal set command (…/set.cpp:517)

Can anyone help me with it?

here is my input script

Displacement Cascade in Fe

-------------- Initialize Simulation ------------

echo both
units metal
dimension 3
boundary p p p
atom_style atomic

neighbor 1.0 bin
neigh_modify delay 0 every 1 check yes

--------------- Creat Atoms / Geometry -----------------------

lattice bcc 2.8665 # bcc lattice spacing 2.8665 Angstrom
region box block 0 25 0 25 0 25
create_box 1 box
create_atoms 1 box basis 1 1 basis 2 1
mass 1 55.847
region rPKA sphere 12.5 12.4 24.5 .1

sphere defined at the top/center of domain, initiate pka down

Note atomic radius Fe = 1.26 A, Nearest Neighbor 1.24 A

masses not necessary ?? for EAM potentials - contained in potential file

------------------Define Interatomic Potential -----------------

pair_style eam/fs
pair_coeff * * Fe_2.eam.fs Fe

Groups

region rallatoms block INF INF INF INF INF INF
region rinterior block 2 23 2 23 2 INF
region rexterior block 2 23 2 23 2 INF side out

group interior region rinterior
group exterior region rexterior
group PKA region rPKA

--------------Initialization----------------

compute 1 all temp
compute 2 interior coord/atom cutoff 2.2
compute 3 interior ke/atom
velocity all create 1200.0 34986

fix 1 all nve # specifiy constant NVE interation to update position andn velocity for atoms in ther group each timestep
fix 2 exterior temp/rescale 1 100.0 100.0 0.5 1.0 region rexterior
fix 3 interior temp/rescale 1 100.0 100.0 0.5 1.0 region rinterior

timestep 0.001
thermo 100
thermo_style custom step temp pe etotal press
run 1000

unfix 3
run 1000

set PKA velocities to correspond to ~ 10keV - 2620.549 Ang/ps

set group PKA vx 109.5108
set group PKA vy 301.1547
set group PKA vz -2600.8815

set timestep to smaller value for initial phase of collision (.01 fs for .2 ps)

timestep 0.00001
thermo 100
dump 1 interior coustom 100 test_init_col.dump x y z c_3 tag type c_2
dump 2 PKA coustom 100 PKA_traj_init_col.dump x y z c_3 tag type c_2
run 20000

run intermediate phase with intermediate timestep (.1 fs for 1 ps)

timestep 0.0001
undump 1
undump 2
dump 3 interior coustom 100 test_inter_evolve.dump x y z c_3 tag type c_2
dump 4 PKA coustom 100 PKA_traj_inter_evolve.dump x y z c_3 tag type c_2
run 10000 # run the collisional phase for .1 ps

run intermediate phase with intermediate timestep (.1 fs for 1 ps)

timestep 0.0001
undump 3
undump 4
timestep 0.001
dump 5 interior coustom 100 test_final_evolve.dump x y z c_3 tag type c_2
dump 6 PKA coustom 100 PKA_traj_final_evolve.dump x y z c_3 tag type c_2
run 10000 # run the collisional phase for .1 ps

Thank you
Mohammad khan

Please check the documentation more carefully. The ‘vx’ keyword is not a supported property of the “set” command (same is true for ‘vy’ and ‘vz’).

Instead you can use the “velocity” command to set the velocity of an atom or a group of atoms.

Axel