Fix SS does not allow use of dynamic group

LAMMPS LAMMPS Beginners
1

Hi,

Would you mind writing any comments how can I overcome this error?

My final goal is to find a viscosity for a region. Is it possible to compute viscosity for a region in Lammps? or does it need to do more calculation for pressure tensor in other software to get the viscosity?

2

a) there is no “fix SS” command in the LAMMPS distribution. Whether that command can be made compatible with dynamic groups would be a question for the developers of that command.

b) viscosity is really more a bulk property and the typical ways to compute it assume that you want to use the entire system to compute it. Limiting it to a region or group opens all kinds of difficult to answer questions about the derivation of the methods you are using that it is not recommended.

3

for example, attached file leads to the mentioned error! is it originated from badly using this command or other reasons?
config.data (2.7 MB)
structure2.in (3.9 KB)

Thanks

4

This is a genuine error. You must not use fix ave/correlate with a dynamic group. That makes no sense at all. How can you correlate data when the dataset keeps changing?