[lammps-users] Help: rigid bond

Dear all,

I have a long polymer chain in nvt ensemble. would you please help me to fix the bonds in my simulation?
what is its command?


If you want the entire molecule to be a rigid body,
then use fix rigid. If you just want the bond lengths
fixed, but it to be otherwise flexible, then the only
LAMMPS option is fix shake. However, fix shake
in LAMMPS is limited to systems where small
clusters of bonds are held fixed but are disjoint
from other clusters. So you can't fix shake on the
backbone bonds of a polymer. This is discussed
on the fix shake doc page. You can also use
rRESPA to have flexible bonds, but still attain
the speed-up that SHAKE offers.