Constraints

Constraints modify how positions and forces are handled by optimizers and molecular dynamics drivers.

Fix atoms

from atomli.constraints import FixAtoms

atoms.set_constraint(FixAtoms(indices=[0, 1]))

Bond constraints

Atomli also exposes FixBondLength, FixBondLengths, FixLinearTriatomic, and Hookean.

Set constraints before creating the optimizer or dynamics driver. Confirm that the attached calculator and selected driver support the constrained workflow.