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doc/compute_ke.html
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<HR>
<H3>compute erotate/sphere command
<H3>compute ke command
</H3>
<P><B>Syntax:</B>
</P>
<PRE>compute ID group-ID erotate/sphere
<PRE>compute ID group-ID ke
</PRE>
<UL><LI>ID, group-ID are documented in <A HREF = "compute.html">compute</A> command
<LI>erotate/sphere = style name of this compute command
<LI>ke = style name of this compute command
</UL>
<P><B>Examples:</B>
</P>
<PRE>compute 1 all erotate/sphere
<PRE>compute 1 all ke
</PRE>
<P><B>Description:</B>
</P>
<P>Define a computation that calculates the rotational kinetic energy of
a group of spherical particles.
<P>Define a computation that calculates the translational kinetic energy
of a group of particles.
</P>
<P>The rotational energy is computed as 1/2 I w^2, where I is the moment
of inertia for a sphere and w is the particle's angular velocity.
<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>IMPORTANT NOTE: For <A HREF = "dimension.html">2d models</A>, particles are treated
as spheres, not disks, meaning their moment of inertia will be the
same as in 3d.
<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>The scalar value calculated by this compute is "extensive", meaning it
it scales with the number of atoms in the simulation.
</P>
<P><B>Restrictions:</B>
<P><B>Restrictions:</B> none
</P>
<P>This compute requires that particles be represented as extended
spheres and not point particles. This means they will have an angular
velocity and a diameter which is determined either by the
<A HREF = "shape.html">shape</A> command or by each particle being assigned an
individual radius, e.g. for <A HREF = "atom_style.html">atom_style granular</A>.
<P><B>Related commands:</B>
</P>
<P><B>Related commands:</B> none
<P><A HREF = "compute_erotate_sphere.html">compute erotate/sphere</A>
</P>
<P><B>Default:</B> none
</P>

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doc/compute_ke.txt
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:line
compute erotate/sphere command :h3
compute ke command :h3
[Syntax:]
compute ID group-ID erotate/sphere :pre
compute ID group-ID ke :pre
ID, group-ID are documented in "compute"_compute.html command
erotate/sphere = style name of this compute command :ul
ke = style name of this compute command :ul
[Examples:]
compute 1 all erotate/sphere :pre
compute 1 all ke :pre
[Description:]
Define a computation that calculates the rotational kinetic energy of
a group of spherical particles.
Define a computation that calculates the translational kinetic energy
of a group of particles.
The rotational energy is computed as 1/2 I w^2, where I is the moment
of inertia for a sphere and w is the particle's angular velocity.
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.
IMPORTANT NOTE: For "2d models"_dimension.html, particles are treated
as spheres, not disks, meaning their moment of inertia will be the
same as in 3d.
There is a subtle difference between the quantity calculated by this
compute and the kinetic energy calculated by the {ke} or {etotal}
keyword used in thermodynamic output, as specified by the
"thermo_style"_thermo_style.html command. For this compute, kinetic
energy is "translational" kinetic energy, calculated by the simple
formula above. For thermodynamic output, the {ke} 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 "compute temp"_compute_temp.html 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).
[Output info:]
The scalar value calculated by this compute is "extensive", meaning it
it scales with the number of atoms in the simulation.
[Restrictions:]
[Restrictions:] none
This compute requires that particles be represented as extended
spheres and not point particles. This means they will have an angular
velocity and a diameter which is determined either by the
"shape"_shape.html command or by each particle being assigned an
individual radius, e.g. for "atom_style granular"_atom_style.html.
[Related commands:]
[Related commands:] none
"compute erotate/sphere"_compute_erotate_sphere.html
[Default:] none