Results of time averaging in a variable?

Hi - I’d like to run an equilibration NPT, take the average box shape, and then use it to run an NVE, in a single lammps input file. Is there any way to get the results of the time averaged box shape (e.g. as computed by “fix ave/time”) in a variable, so I can use it in a change box command? All I’ve been able to get from the documentation and searching the mailing list is how to write it to a file.

              thanks,
              Noam

Have you tried something like:

“variable var equal f_ave”

where “ave” is an ID of fix ave/time?

Michal

Hi - I’d like to run an equilibration NPT, take the average box shape, and
then use it to run an NVE, in a single lammps input file. Is there any way
to get the results of the time averaged box shape (e.g. as computed by “fix
ave/time”) in a variable, so I can use it in a change box command? All
I’ve been able to get from the documentation and searching the mailing list
is how to write it to a file.

​from the fix ave/time documentation:

​Restart, fix_modify, output, run start/stop, minimize info:

No information about this fix is written to binary restart files. None of
the fix_modify options are relevant to this fix.

**This fix produces a global scalar or global vector or global array which
can be accessed by various output commands. The values can only be accessed
on timesteps that are multiples of Nfreq since that is when averaging is
performed.**

axel.

Thanks - I eventually realized that I can use “f_ID” to refer to fix results. I think my problem is that I don’t really have a top level view of the entities in lammps, since I’ve mostly operated by reading docs/examples and trying to glean the underlying general concepts (i.e. the direct statement that you can in general refer to the results of fixes as “f_ID”). Maybe I just need to go back and do a basic tutorial, but the ones I’ve found have been too basic for this.

Noam

Two suggestions:

a) Section_howto 6.15 describes all the ways the output
of one command can be used as input to another

b) The variable doc page is a comprehensive list of
all the things you can do with variables.

Steve