Tabulated External Force

This force module enables the possibility of using a precalculated external potential. This can be useful if the external potential is known and does not change in time. The interpolation points are distributed on a uniform grid and must be calculated before usage.

Depending on the interpolation scheme, more than just the potential values will be needed. If the scheme needs coefficients that can be calculated from the derivatives of the potential, halmd.mdsim.forces.tabulated_generator can be used for the calculation of the coefficients.

Note

Particle species are unsupported, all particles from the given halmd.mdsim.particle instance are treated equally.

class halmd.mdsim.forces.tabulated_external(args)

Construct tabulated external force.

Parameters:

• args (table) – keyword arguments
• args.particle – instance of halmd.mdsim.particle
• args.box – instance of halmd.mdsim.box
• args.interpolation – instance of halmd.mdsim.forces.interpolation
• args.virial_interpolation – instance of halmd.mdsim.forces.interpolation

Returns:

instance of tabulated_external force module

set_coefficients(coefficients)

Set the interpolation coefficients as needed by the scheme

Parameters:coefficients (table) – coefficients as needed by the interpolation scheme

read_coefficients(args)

Read interpolation coefficients for external force from file.

Parameters:

• args (table) – keyword arguments
• args.file – instance of file reader
• args.location (string table) – location within file (optional)

The argument location specifies a path in a structured file format like H5MD given as a table of strings. If omitted it defaults to {"parameters/halmd"}.

disconnect()

Disconnect force from profiler and particle module.