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# compute erotate/sphere command

Accelerator Variants: erotate/sphere/kk

## Syntax

    compute ID group-ID erotate/sphere

- ID, group-ID are documented in compute command

- erotate/sphere = style name of this compute command

## Examples

    compute 1 all erotate/sphere

## Description

Define a computation that calculates the rotational kinetic energy of a group of spherical particles.

The rotational energy is computed as \(\frac12 I \omega^2\), where \(I\) is the moment of inertia for a sphere and \(\omega\) is the particle’s angular velocity.

Note

For 2d models, particles are treated as spheres, not disks, meaning their moment of inertia will be the same as in 3d.

Styles with a gpu, intel, kk, omp, or opt suffix are functionally the same as the corresponding style without the suffix. They have been optimized to run faster, depending on your available hardware, as discussed on the Accelerator packages page. The accelerated styles take the same arguments and should produce the same results, except for round-off and precision issues.

These accelerated styles are part of the GPU, INTEL, KOKKOS, OPENMP, and OPT packages, respectively. They are only enabled if LAMMPS was built with those packages. See the Build package page for more info.

You can specify the accelerated styles explicitly in your input script by including their suffix, or you can use the -suffix command-line switch when you invoke LAMMPS, or you can use the suffix command in your input script.

See the Accelerator packages page for more instructions on how to use the accelerated styles effectively.

## Output info

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 the Howto output page for an overview of LAMMPS output options.

The scalar value calculated by this compute is “extensive”. The scalar value will be in energy units.

## Restrictions

This compute requires that atoms store a radius and angular velocity (omega) as defined by the atom_style sphere command.

All particles in the group must be finite-size spheres or point particles. They cannot be aspherical. Point particles will not contribute to the rotational energy.

## Related commands

compute erotate/asphere

## Default

none