# fix_modify AtC boundary_dynamics

## syntax

fix_modify AtC boundary_dynamics < on | damped_harmonic | prescribed | coupled | none > [args]

## description

Sets different schemes for controlling boundary atoms. On will integrate the boundary atoms using the velocity-verlet algorithm. Damped harmonic uses a mass/spring/dashpot for the boundary atoms with added arguments of the damping and spring constants followed by the ratio of the boundary type mass to the desired mass. Prescribed forces the boundary atoms to follow the finite element displacement. Coupled does the same.

## restrictions

Boundary atoms must be specified. When using swaps between internal and boundary atoms, the initial configuration must have already correctly partitioned the two.

## related

## default

prescribed on