fix

This keyword can be used to fix (freeze) a group of atoms

Syntax

This keyword accepts 1 or 2 parameters. The atoms in the specified group will be fixed (velocities and forces are always set to zero such that the atoms do not move). The full command reads:

fix <group_label>
fix <grouping_method> <group_label>

• If only group_label is given, grouping method 0 is used by default.

• If grouping_method is also specified, the given grouping method defined in the simulation model file will be used.

Example

Fix group 0 using the default grouping method 0:

fix 0

Fix group 2 using grouping method 1:

fix 1 2

Caveats

• This keyword is not propagating, which means that it only affects the simulation within the run it belongs to.

• When both fix and move are used, they must use the same grouping method.