# steering_force

Apply a harmonic steering force on a collective variable for a specified time sequence during a molecular dynamics simulation.

The reference value and force constant of the moving restraint within each time window are linearly interpolated based on the initial and final values of that time window.

This command can appear in the global context.

### Options

force_constants

The sequence of force constants, with each element corresponds to the value of force constant at each time point specified in time_sequence, respectively.

The total number of elements must be equivalent to the number of elements in time_sequence.

The unit of the input values are atomic unit.

If the collective variable is a position, the allowed number of elements must be two.

• The type is [real]
• There is no default value.
reference_values

The sequence of reference values for the harmonic restraint, with each element corresponds to the reference value at each time point in time_sequence.

The total number of elements must be equivalent to the number of elements in time_sequence.

The unit of the input values depends on the coordinate type: for distance, the values are in angstroms; for angle and dihedral, the values are in degrees.

This option cannot be used for the position coordinate. For position based steering forces, one has to specify initial and final xyz coordinates.

• The type is [real]
• There is no default value.
time_sequence

The time sequence with which the steering force is applied. The values for this option is a list of real numbers, corresponding to the starting/ending time for each time window.

The input values are in the unit of picoseconds.

If the collective variable is a position, the allowed number of elements must be two.

• The type is [real]
• There is no default value.