move

This keyword is used to move part of the system with a constant velocity.

Syntax

The move keyword accepts 4 or 5 parameters:

move <moving_group_id> <velocity_x> <velocity_y> <velocity_z>
move <grouping_method> <moving_group_id> <velocity_x> <velocity_y> <velocity_z>

  • If only moving_group_id and velocities are 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.

The last three parameters specify the moving velocity vector, in units of Ångstrom/fs.

Example

One can first equilibrate the system and then move one group of atoms and at the same time fix another group of atoms:

# equilibration stage
ensemble npt_scr 300 300 100 0 0 0 100 100 100 1000
run 1000000

# production stage
ensemble nvt_ber 300 300 100
fix  0            # fix atoms in group 0 (default grouping method 0)
move 1 0.001 0 0  # move atoms in group 1, with a speed of 0.001 Ångstrom/fs in the x direction (default grouping method 0)
run  1000000

Using a specific grouping method:

ensemble nvt_ber 300 300 100
fix  1 0            # fix group 0 in grouping method 1
move 1 1 0.001 0 0  # move group 1 in grouping method 1, with a speed of 0.001 Ångstrom/fs in the x direction
run  1000000

Caveats

  • One cannot use NPT when using this keyword. Only nvt_ber, nvt_nhc, nvt_bdp, and heat_lan ensembles are supported.

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