Some question about fix ave/correlate command

LAMMPS LAMMPS Beginners
1

Dear All,
I am beginner and hereby read the ave/correlate documentation. However, I have some questions about this command.

  1. For fix SS command, does f_SS[3] mean the auto correlation of v_pxy?? ( because I confused whether the first column is [0] or [1] in lammps)
fix SS all ave/correlate $s $p $d &
v_pxy v_pxz v_pyz v_pxx v_pyy v_pzz type auto file S0St.dat ave running

variable  v11 equal trap(f_SS[3])*${scale}

  1. Is there any suggestion to use dynamic group with ave/correlation command? for example, store the variable and then start the auto correlation?

  2. Does above command work the same as Statsmoldels library of Python (acf) for computing the auto correlation?

Thanks

2
  1. indexes in LAMMPS input scripts are 1-based.
  2. you must not use this fix with a dynamic group.
  3. no idea. What the fix does is described in the documentation.
3

indexes in LAMMPS input scripts are 1-based.

So, I cannot understand why is f_SS[3] referred to forth column of fix SS at below LAMMPS documentation? Is there some misunderstanding by my side?
https://docs.lammps.org/Howto_viscosity.html

fix          SS all ave/correlate $s $p $d &
             v_pxy v_pxz v_pyz type auto file S0St.dat ave running
variable     v11 equal trap(f_SS[3])*${scale}

Thanks for clarification

4

Yes, please see the documentation of fix ave/correlate what it computes and how its output is organized.

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