how to use rigid bodies?

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1

hi
dear all
i have a mulecule which i want to take it as a rigid bodey i used the fix
rigid command to do so but when i runed the system my molecule is both
rigid and fixed in it's initial coordiates. i want it to move as a rigid
bodey.how can i do that ?
thanks

2

hi
dear all
i have a mulecule which i want to take it as a rigid bodey i used the fix
rigid command to do so but when i runed the system my molecule is both
rigid and fixed in it's initial coordiates. i want it to move as a rigid
bodey.how can i do that ?

​impossible to say without any information about what you did.​

​the fix rigid documentation contains explanations for how to use it and
the examples/rigid directory contains examples. they all work, so you must
be doing something wrong.

​axel.​

3
4

fix 3 c60 rigid/small molecule langevin 1.0 1.0 1.0 428984

5

> fix 3 c60 rigid/small molecule langevin 1.0 1.0 1.0 428984
> fix 1 all npt temp 300.0 300.0 100.0 iso 1 1 1000

These lines are applying 2 thermostats and 2 time integrators to
the same particles. Which is bad. You should have got
a WARNING from LAMMPS that you are time integrating
twice. The fix rigid doc page has a section about how to do constant
pressure with rigid bodies. You need to follow what it says.

​furthermore, the langevin thermostat is set to thermalize at 1K. not much
can happen at that temperature anyway.

GI-GO,
    axel.

6

thanks Mr kohlmer