# compute erotate/sphere command

## 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 1/2 I w^2, where I is the moment of inertia for a sphere and w 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.

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 doc 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.