compute dipole command

Syntax

compute ID group-ID dipole charge-correction

• ID, group-ID are documented in compute command

• dipole = style name of this compute command

• charge-correction = mass or geometry, use COM or geometric center for charged chunk correction (optional)

Examples

compute 1 fluid dipole
compute dw water dipole geometry

Description

Define a computation that calculates the dipole vector and total dipole for a group of atoms.

This compute calculates the x,y,z coordinates of the dipole vector and the total dipole moment for the atoms in the compute group. This includes all effects due to atoms passing through periodic boundaries. For a group with a net charge the resulting dipole is made position independent by subtracting the position vector of the center of mass or geometric center times the net charge from the computed dipole vector. Both per-atom charges and per-atom dipole moments, if present, contribute to the computed dipole.

Note

The coordinates of an atom contribute to the dipole in “unwrapped” form, by using the image flags associated with each atom. See the dump custom command for a discussion of “unwrapped” coordinates. See the Atoms section of the read_data command for a discussion of image flags and how they are set for each atom. You can reset the image flags (e.g. to 0) before invoking this compute by using the set image command.

Output info

This compute calculations a global scalar containing the magnitude of the computed dipole moment and a global vector of length 3 with the dipole vector. See the Howto output page for an overview of LAMMPS output options.

The computed values are “intensive”. The array values will be in dipole units, i.e. charge units times distance units.

Restrictions

none

Related commands

compute dipole/chunk

Default

Using the center of mass is the default setting for the net charge correction.