Save coordinate of an atom AT A GIVEN TIME: how ?

Dear all,

I am making simulations of deposition.

For this I need to save the initial z coordinate of the deposited atom.

I have been using:

variable z_dep equal “z[v_id_deposited_now]”

So in the variable z_dep is the z coordinate of the additional atom.

The problem is that during the evolution this atoms change position and,
with it, the value of the variable z_dep.

But this is not what I need.

How can I save in memory the value of this coordinate AT THE BEGINNING, so that its value does not change with time ?

I need to access this value at a later stage.

Many thanks in advance for your help

Bests,

Daniele Scopece

PS: for completeness I have been using the fix
fix id_depositing all deposit {N_atoms_deposited} 1 {N_step_depositing} 1234567890 &
region reg_deposition global 1.0 1.5 vx 0.0 0.0 vy 0.0 0.0 vz -{proj_vel_Angpsec} -{proj_vel_Angpsec} &
units box

with variables defined above in the script.

The variable doc page has a section on how to

do this, near the bottom.

Steve