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### fix efield command

Syntax:

    fix ID group-ID efield ex ey ez

- ID, group-ID are documented in fix command
- efield = style name of this fix command
- ex,ey,ez = E-field component values (electric field units)
- any of ex,ey,ez can be a variable (see below)

Examples:

    fix kick external-field efield 1.0 0.0 0.0
    fix kick external-field efield 0.0 0.0 v_oscillate

Description:

Add a force F = qE to each charged atom in the group due to an external electric field being applied to the system.

Any of the 3 quantities defining the E-field components can be specified as an equal-style or atom-style variable, namely ex, ey, ez. If the value is a variable, it should be specified as v_name, where name is the variable name. In this case, the variable will be evaluated each timestep, and its value used to determine the E-field component.

Equal-style variables can specify formulas with various mathematical functions, and include thermo_style command keywords for the simulation box parameters and timestep and elapsed time. Thus it is easy to specify a time-dependent E-field.

Atom-style variables can specify the same formulas as equal-style variables but can also include per-atom values, such as atom coordinates. Thus it is easy to specify a spatially-dependent E-field with optional time-dependence as well.

Restart, fix_modify, output, run start/stop, minimize info:

No information about this fix is written to binary restart files. None of the fix_modify options are relevant to this fix. No global or per-atom quantities are stored by this fix for access by various output commands. No parameter of this fix can be used with the start/stop keywords of the run command. This fix is not invoked during energy minimization.

Restrictions: none

Related commands:

fix addforce

Default: none