compute erotate/sphere command

Syntax

compute ID group-ID erotate/sphere general_keywords general_values halfstep

ID, group-ID are documented in compute command
erotate/sphere = style name of this compute command
general_keywords general_values are documented in compute
halfstep = optional keyword to compute energy at half step

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

$E_{rot} = \frac{1}{2} I \omega^2$

where $I$ is the moment of inertia for a sphere and $\omega$ is the absolute value of the particle’s angular velocity. By default the angular velocity is taken at the full time step ( $\omega_i$ ). If the halfstep keyword is present in the definition of this compute, then the angular velocity is taken at the next half time step ( $\omega_{i+\frac{1}{2}}$ ).

Warning

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 Section_howto 15 for an overview of Aspherix® 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.