next set of converted AtC documentation

.. index:: fix_modify AtC control momentum

fix_modify AtC control momentum command

=======================================

Syntax

""""""

.. parsed-literal::

   fix_modify <AtC fixID> control <physics_type> <solution_parameter> <value>

   fix_modify AtC control momentum none

   fix_modify AtC control momentum rescale <frequency>

   fix_modify AtC control momentum glc_displacement

   fix_modify AtC control momentum glc_velocity

   fix_modify AtC control momentum hoover

   fix_modify AtC control momentum flux [faceset face_set_id, interpolate]

* AtC fixID = ID of :doc:`fix atc <fix_atc>` instance

* control = name of the AtC sub-command

* physics_type = *thermal* or *momentum*

* solution_parameter = *max_iterations* or *tolerance*

* value = solution_parameter value

* momentum option = *none* or *rescale* or *glc_displacement* or *glc_velocity* *hoover* or *flux*

* frequency = time step frequency for applying displacement and velocity rescaling

* faceset_id = id of boundary face set (optional, only for *faceset*)

Examples

""""""""

.. code-block:: LAMMPS

   fix_modify AtC control momentum none

   fix_modify AtC control momentum flux faceset bndy_faces

   fix_modify AtC control momentum glc_velocity

Description

"""""""""""

The general version of *control* sets the numerical parameters for the

matrix solvers used in the specified control algorithm.  Many solution

approaches require iterative solvers, and these methods enable users to

provide the maximum number of iterations and the relative tolerance.

The *control momentum* version sets the momentum exchange mechanism from

the finite elements to the atoms, managed through a control algorithm.

*rescale* computes a scale factor for each atom to match the finite

element temperature.  *hoover* is a Gaussian least-constraint isokinetic

thermostat enforces that the nodal restricted atomic temperature matches

the finite element temperature.  *flux* is a similar mode, but rather

adds energy to the atoms based on conservation of energy.

*correction_max_iterations* sets the maximum number of iterations to

compute the 2nd order in time correction term for lambda with the

fractional step method. The method uses the same tolerance as the

controller's matrix solver.

Restrictions

""""""""""""

Only for be used with the specific controllers *thermal* or *momentum*.

They are ignored if a lumped solution is requested.

*control momentum* is only for be used with specific transfers: elastic

*rescale* not valid with time filtering activated

Related AtC commands

""""""""""""""""""""

:doc:`fix_modify AtC control thermal <atc_control_thermal>`

Default

"""""""

- *max_iterations* is the number of rows in the matrix.

- *tolerance* is 1.0e-10.

.. index:: fix_modify AtC control thermal

fix_modify AtC control thermal command

======================================

Syntax

""""""

.. parsed-literal::

   fix_modify <AtC fixID> control <physics_type> <solution_parameter> <value>

   fix_modify <AtC fixID> control thermal <control_type> <optional_args>

   fix_modify <AtC fixID> control thermal rescale <frequency>

   fix_modify <AtC fixID> control thermal flux <boundary_integration_type> <faceset_id>

   fix_modify <AtC fixID> control thermal correction_max_iterations <max_iterations>

* AtC fixID = ID of :doc:`fix atc <fix_atc>` instance

* control = name of the AtC sub-command

* physics_type = *thermal* or *momentum*

* solution_parameter = *max_iterations* or *tolerance*

* value = solution_parameter value

* thermal control_type = *none* or *rescale* or *hoover* or *flux*

* frequency = time step frequency for applying velocity rescaling

* boundary_integration_type = *faceset* or *interpolate* (optional)

* faceset_id = id of boundary face set (optional, only for *faceset*)

* correction_max_iterations = maximum number of iterations that will be used by iterative matrix solvers for *thermal* physics type

Examples

""""""""

.. code-block:: LAMMPS

   fix_modify AtC control thermal none

   fix_modify AtC control thermal rescale 10

   fix_modify AtC control thermal hoover

   fix_modify AtC control thermal flux

   fix_modify AtC control thermal flux faceset bndy_faces

   fix_modify AtC control thermal correction_max_iterations 10

Description

"""""""""""

The general version of *control* sets the numerical parameters for the

matrix solvers used in the specified control algorithm.  Many solution

approaches require iterative solvers, and these methods enable users to

provide the maximum number of iterations and the relative tolerance.

The *control thermal* version sets the energy exchange mechanism from

the finite elements to the atoms, managed through a control algorithm.

*rescale* computes a scale factor for each atom to match the finite

element temperature.  *hoover* is a Gaussian least-constraint isokinetic

thermostat enforces that the nodal restricted atomic temperature matches

the finite element temperature.  *flux* is a similar mode, but rather

adds energy to the atoms based on conservation of energy. *hoover* and

*flux* allow the prescription of sources or fixed temperatures on the

atoms.

*correction_max_iterations* sets the maximum number of iterations to

compute the 2nd order in time correction term for lambda with the

fractional step method. The method uses the same tolerance as the

controller's matrix solver.

Restrictions

""""""""""""

Only for be used with the specific controllers *thermal* or *momentum*.

They are ignored if a lumped solution is requested.

*control thermal* is only for be used with specific transfers: thermal (*rescale*\ , *hoover*\ , *flux*\ ), *two_temperature* (*flux*\ ).

*rescale* not valid with time filtering activated

*correction_max_iterations* is only for use with *thermal* physics using

the fractional step method.

Related AtC commands

""""""""""""""""""""

:doc:`fix_modify AtC control momentum <atc_control_momentum>`

Default

"""""""

- *max_iterations* is the number of rows in the matrix.

- *tolerance* is 1.0e-10.

- *rescale* frequency is 1

- *flux* boundary_integration_type is *interpolate*

- *correction_max_iterations* is 20

.. index:: fix_modify AtC fix

fix_modify AtC initial command

==============================

fix_modify AtC fix command

==========================

Syntax

""""""

.. index:: fix_modify AtC fix_flux

fix_modify AtC fix_flux command

===============================

Syntax

""""""

.. parsed-literal::

   fix_modify <AtC fixID> fix_flux <field> <face_set> <value|function>

* AtC fixID = ID of :doc:`fix atc <fix_atc>` instance

* fix_flux = name of the AtC sub-command

* field = field kind name valid for type of physics: *temperature* or *electron_temperature*

* face_set = name of set of element faces

* *value* or *function* = value or name of function followed by its parameters

Examples

""""""""

.. code-block:: LAMMPS

   fix_modify AtC fix_flux temperature faceSet 10.0

Description

"""""""""""

Command for fixing normal fluxes e.g. heat_flux. This command only

prescribes the normal component of the physical flux, e.g. heat (energy)

flux. The units are in AtC units, i.e. derived from the LAMMPS length,

time, and mass scales.

Restrictions

""""""""""""

Only normal fluxes (Neumann data) can be prescribed.

Related AtC commands

""""""""""""""""""""

:doc:`fix_modify AtC unfix_flux <atc_unfix_flux>`

Default

"""""""

None.

Eulerian reset frequency must be an integer multiple of the Lammps

reneighbor frequency.

Related AtC Sub-commands

""""""""""""""""""""""""

Related AtC commands

""""""""""""""""""""

- :doc:`fix_modify AtC atom_element_map <atc_atom_element_map>`

- :doc:`fix_modify AtC boundary type <atc_boundary_type>`