Syntax:
-compute ID group-ID erotate/sphere +compute ID group-ID ke
Examples:
-compute 1 all erotate/sphere +compute 1 all keDescription:
-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, 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 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 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 command or by each particle being assigned an -individual radius, e.g. for atom_style granular. +
Related commands:
-Related commands: none +
Default: none
diff --git a/doc/compute_ke.txt b/doc/compute_ke.txt index 1ee0bbce80..53d8527d2a 100644 --- a/doc/compute_ke.txt +++ b/doc/compute_ke.txt @@ -6,44 +6,49 @@ :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