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rLAMMPS lammps
compute_ke.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>
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 or 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 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#4_15"
>
this section
</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>
</HTML>
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