# Velocity set

Hi,

I try to simulate the irradiation, but there is sth wrong with the velocity, the details please below,

region 1 block INF INF INF 22 INF INF units box
region 2 block INF INF 175 INF INF INF units box
region 3 block INF 22 22 175 INF INF units box
region 4 block 177 INF 22 175 INF INF units box

region boundary union 4 1 2 3 4

group boundary region boundary
group id id 260484

pair_style vashishta
pair_coeff * * Al2O3.vashishta O Al

timestep 0.001

velocity id set 0 0 -1890 sum yes units box
fix 11 boundary nvt temp 1 1 1 drag 1

run 200000

The atom id 260484 is one atom in the surface centre, and i want to give this atom velocity use the common “velocity id set 0 0 -1890 sum yes units box”, but i find that there is no speed toward this atom, so could you please help me find the reason? Thanks for your help.

Hi,

I try to simulate the irradiation, but there is sth wrong with the

region 1 block INF INF INF 22 INF INF units box
region 2 block INF INF 175 INF INF INF units box
region 3 block INF 22 22 175 INF INF units box
region 4 block 177 INF 22 175 INF INF units box

region boundary union 4 1 2 3 4

group boundary region boundary
group id id 260484

pair_style vashishta
pair_coeff * * Al2O3.vashishta O Al

timestep 0.001

velocity id set 0 0 -1890 sum yes units box
fix 11 boundary nvt temp 1 1 1 drag 1

run 200000

The atom id 260484 is one atom in the surface centre, and i want to give
this atom velocity use the common "velocity id set 0 0 -1890 sum yes units
box", but i find that there is no speed toward this atom, so could you