Constraint atom motion in LAMMPS
Suppose if one creates a dislocation in a system with two surfaces top and bottom on z axis and periodic in x and y axes. Motions of atoms at the top and bottom layer should be limited along x and y direction and not to move z direction. One can achieve this constraint in LAMMPS by writing as follows, :
region top block 0.0 300.0 0.0 20.0 212.643446964 300.0 region bottom block 0.0 300.0 0.0 20.0 0.0 7.0 group topatoms region top group botatoms region bottom fix constraint topatoms setforce NULL NULL 0.0 fix constraint botatoms setforce NULL NULL 0.0 velocity all set 0.0 0.0 0.0
Here two regions are defined, called
bottom. Then groups of
botatoms are defined, and the forces of z
component are reset to 0.