[lammps-users] fix shake for molecule without bond

Hi Lammps users,

I am trying to use fix shake to maintain the molecule shape of H2. However, the force field given by literature does not include a bond between two H atoms. But the fix shake method works only for bond and angle. In this case, is there any method to use fix shake in this force field?

Regards,
Michael

For fix shake to work, it needs to know what distance should be between the two atoms and that is taken from the bond coefficients.
It can be pretty much any kind of bond style, including bond style zero. The force constant will be ignored anyway.

Other than that, you could use fix rigid, but that usually requires a much shorter timestep than when using fix shake and thus is quite wasteful.

axel.

Thank you, Axel, for your kind help. It is exactly what I need.

Thanks,
Michael