[lammps-users] fix shake and fix rigid command

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Dear Lammps Users,

I have a question about the ‘fix shake’ and ‘fix rigid’ command of Lammps. To calculate the motion of benzene, I really want to constrain the bonds and the angles of the benzene, but if I used the shake command, I got some error message 'Shake clusters are connected’. And I also tried to make the benzene molecule rigid body, but I cannot use nvt and npt. Specifically, when I applied the TraPPE-UA force field, I really need these two fix commands, but right now I don’t have any clue. If anyone have some ideas, please give some advice to me. Thank you.

Seung Ha Kim

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You can't do a ring like benzene with the fix shake in LAMMPS. You
can use fix rigid, but you should probably thermostat the benzene rings
(or any other rigid body) with fix langevin. You could thermostat
other atoms or the system with fix nvt or npt.

Steve