File: fix_efield.html

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<HTML>
<CENTER><A HREF = "http://lammps.sandia.gov">LAMMPS WWW Site</A> - <A HREF = "Manual.html">LAMMPS Documentation</A> - <A HREF = "Section_commands.html#comm">LAMMPS Commands</A> 
</CENTER>






<HR>

<H3>fix efield command 
</H3>
<P><B>Syntax:</B>
</P>
<PRE>fix ID group-ID efield ex ey ez 
</PRE>
<UL><LI>ID, group-ID are documented in <A HREF = "fix.html">fix</A> command
<LI>efield = style name of this fix command
<LI>ex,ey,ez = E-field component values (electric field units)
<LI>any of ex,ey,ez can be a variable (see below) 
</UL>
<P><B>Examples:</B>
</P>
<PRE>fix kick external-field efield 1.0 0.0 0.0
fix kick external-field efield 0.0 0.0 v_oscillate 
</PRE>
<P><B>Description:</B>
</P>
<P>Add a force F = qE to each charged atom in the group due to an
external electric field being applied to the system.
</P>
<P>Any of the 3 quantities defining the E-field components can be
specified as an equal-style or atom-style <A HREF = "variable.html">variable</A>,
namely <I>ex</I>, <I>ey</I>, <I>ez</I>.  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.
</P>
<P>Equal-style variables can specify formulas with various mathematical
functions, and include <A HREF = "thermo_style.html">thermo_style</A> command
keywords for the simulation box parameters and timestep and elapsed
time.  Thus it is easy to specify a time-dependent E-field.
</P>
<P>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.
</P>
<P><B>Restart, fix_modify, output, run start/stop, minimize info:</B>
</P>
<P>No information about this fix is written to <A HREF = "restart.html">binary restart
files</A>.  None of the <A HREF = "fix_modify.html">fix_modify</A> options
are relevant to this fix.  No global or per-atom quantities are stored
by this fix for access by various <A HREF = "Section_howto.html#howto_15">output
commands</A>.  No parameter of this fix can
be used with the <I>start/stop</I> keywords of the <A HREF = "run.html">run</A> command.
This fix is not invoked during <A HREF = "minimize.html">energy minimization</A>.
</P>
<P><B>Restrictions:</B> none
</P>
<P><B>Related commands:</B>
</P>
<P><A HREF = "fix_addforce.html">fix addforce</A>
</P>
<P><B>Default:</B> none
</P>
</HTML>