time averaging of stress computed by atc package

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1

Dear LAMMPS community,

I have a question regarding time averaging of the computed local stress using atc package. I want to calculate the local stress in an amorphous system under shear using Hardy’s implementation of Irving-kirkwood stress. Since there are, definitely, temporal fluctuations, I would like to average the local stress over short time intervals. If there is no averaging, I can save the configurations and calculate the stress by my own code! Is there any fix_modify for this purpose?

Best regards,

Reza

2

There are several fix ave commands, like fix ave/time, fix ave/atom, etc.

They are all designed to take input from other commands which produce

output.

Steve

3

Dear Steve,

I know about those fixes but the atc calculated stress is neither per_atom property nor a global value. Therefore, none of the fixes mentioned could be used. Atc package outputs the stress according to a mesh created and (I think) return an instantaneous property via a “fix_modify output” command. My question is how this could return a time-averaged value instead of an instantaneous value.

best regards

4

hi Muhammad
you can get time-averages of the nodal/spatial averaged field data by adding
fix_modify ATC filter on
fix_modify ATC filter scale 5.0e2
where the last float is the timescale of a running, causal filter with an exponential kernel
if you want just a running average

fix_modify ATC filter on
fix_modify ATC filter type step

should work
Reese