# compute erotate/multisphere command

## Syntax

    compute ID group-ID erotate/multisphere general_keyword general_values

- ID, group-ID are documented in compute command
- erotate/multisphere = style name of this compute command
- general_keywords general_values are documented in compute

## Examples

    compute 1 all erotate/multisphere

## Description

Define a computation that calculates the rotational kinetic energy of a collection of multisphere bodies.

The rotational energy of each multisphere body is computed as 1/2 I Wbody^2, where I is the inertia tensor for the multisphere body, and Wbody is its angular velocity vector. Both I and Wbody are in the frame of reference of the multisphere body, i.e. I is diagonalized.

This compute automatically connects to the fix multisphere commands which defines the multisphere bodies. The group specified in the compute command is ignored. The rotational energy of all the multisphere bodies defined by the fix multisphere command in included in the calculation.

## Output info

This compute calculates a global scalar (the summed rotational energy of all the multisphere bodies). This value can be used by any command that uses a global scalar value from a compute as input. See Section_howto 15 for an overview of LIGGGHTS(R)-PUBLIC output options.

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

## Restrictions

> none

## Related commands

`compute ke/multisphere`

Default: none