.. index:: fix_modify AtC rates

fix_modify AtC rates command
================================

Syntax
""""""

.. code-block:: LAMMPS

   fix_modify <AtC fixID> rates <add|delete> <list_of_fields>

* AtC fixID = ID of :doc:`fix atc <fix_atc>` instance
* rates = name of the AtC sub-command
* *add* or *delete* = select whether to add or delete calculation of rates for the listed output fields
* list_of_fields = one or more of the fields listed below:

  - density : mass per unit volume
  - displacement : displacement vector
  - momentum : momentum per unit volume
  - velocity : defined by momentum divided by density
  - projected_velocity : simple kernel estimation of atomic velocities
  - temperature : temperature derived from the relative atomic kinetic energy
  - kinetic_temperature : temperature derived from the full kinetic energy
  - number_density : simple kernel estimation of number of atoms per unit volume
  - stress : Cauchy stress tensor for eulerian analysis (atom_element_map), or first Piola-Kirchhoff stress tensor for lagrangian analysis
  - transformed_stress : first Piola-Kirchhoff stress tensor for eulerian analysis (atom_element_map), or Cauchy stress tensor for lagrangian analysis
  - heat_flux : spatial heat flux vector for eulerian, or referential heat flux vector for lagrangian
  - potential_energy : potential energy per unit volume
  - kinetic_energy : kinetic energy per unit volume
  - thermal_energy : thermal energy (kinetic energy - continuum kinetic energy) per unit volume
  - internal_energy : total internal energy (potential + thermal) per unit volume
  - energy : total energy (potential + kinetic) per unit volume
  - number_density : number of atoms per unit volume
  - eshelby_stress : configurational stress (energy-momentum) tensor defined by [Eshelby]_
  - vacancy_concentration : volume fraction of vacancy content
  - type_concentration : volume fraction of a specific atom type


Examples
""""""""

.. code-block:: LAMMPS

   fix_modify AtC rates add temperature velocity stress
   fix_modify AtC rates delete stress


Description
"""""""""""

Requests calculation and output of rates (time derivatives) of the
fields from the AtC transfer class.  For Eulerian analysis (see
:doc:`fix_modify AtC atom_element_map <atc_atom_element_map>`) these
rates are the partial time derivatives of the nodal fields, not the full
(material) time derivatives.

Restrictions
""""""""""""

Must be used with :doc:`fix atc hardy <fix_atc>`.

Related AtC commands
""""""""""""""""""""

- :ref:`fix_modify AtC command overview <atc_fix_modify>`
- :doc:`fix_modify AtC atom_element_map <atc_atom_element_map>`
- :doc:`fix_modify AtC fields <atc_hardy_fields>`
- :doc:`fix_modify AtC fields <atc_hardy_gradients>`

Default
"""""""

None.
