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compute_ke.html
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<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>compute ke command
</H3>
<P><B>Syntax:</B>
</P>
<PRE>compute ID group-ID ke
</PRE>
<UL><LI>ID, group-ID are documented in <A HREF = "compute.html">compute</A> command
<LI>ke = style name of this compute command
</UL>
<P><B>Examples:</B>
</P>
<PRE>compute 1 all ke
</PRE>
<P><B>Description:</B>
</P>
<P>Define a computation that calculates the translational kinetic energy
of a group of particles.
</P>
<P>The kinetic energy of each particle is computed as 1/2 m v^2, where m
and v are the mass and velocity of the particle.
</P>
<P>There is a subtle difference between the quantity calculated by this
compute and the kinetic energy calculated by the <I>ke</I> or <I>etotal</I>
keyword used in thermodynamic output, as specified by the
<A HREF = "thermo_style.html">thermo_style</A> command. For this compute, kinetic
energy is "translational" kinetic energy, calculated by the simple
formula above. For thermodynamic output, the <I>ke</I> keyword infers
kinetic energy from the temperature of the system with 1/2 Kb T of
energy for each degree of freedom. For the default temperature
computation via the <A HREF = "compute_temp.html">compute temp</A> command, these
are the same. But different computes that calculate temperature can
subtract out different non-thermal components of velocity and/or
include different degrees of freedom (translational, rotational, etc).
</P>
<P><B>Output info:</B>
</P>
<P>This compute calculates a global scalar (the summed KE). This value
can be used by any command that uses a global scalar value from a
compute as input. See <A HREF = "Section_howto.html#howto_15">Section_howto 15</A>
for an overview of LAMMPS output options.
</P>
<P>The scalar value calculated by this compute is "extensive". The
scalar value will be in energy <A HREF = "units.html">units</A>.
</P>
<P><B>Restrictions:</B> none
</P>
<P><B>Related commands:</B>
</P>
<P><A HREF = "compute_erotate_sphere.html">compute erotate/sphere</A>
</P>
<P><B>Default:</B> none
</P>
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