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lammps/doc/fix_shardlow.rst
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.. index:: fix shardlow
fix shardlow command
====================
Syntax
""""""
.. parsed-literal::
fix ID group-ID shardlow
* ID, group-ID are documented in :doc:`fix <fix>` command
* shardlow = style name of this fix command
Examples
""""""""
.. parsed-literal::
fix 1 all shardlow
Description
"""""""""""
Specifies that the Shardlow splitting algorithm (SSA) is to be used to
integrate the DPD equations of motion. The SSA splits the integration
into a stochastic and deterministic integration step. The fix
*shardlow* performs the stochastic integration step and must be used
in conjunction with a deterministic integrator (e.g. :doc:`fix nve <fix_nve>` or :doc:`fix nph <fix_nph>`). The stochastic
integration of the dissipative and random forces is performed prior to
the deterministic integration of the conservative force. Further
details regarding the method are provided in :ref:`(Lisal) <Lisal>` and
:ref:`(Larentzos) <Larentzos>`.
The fix *shardlow* must be used with the :doc:`pair_style dpd/fdt <pair_style>` or :doc:`pair_style dpd/fdt/energy <pair_style>` command to properly initialize the
fluctuation-dissipation theorem parameter(s) sigma (and kappa, if
necessary).
Note that numerous variants of DPD can be specified by choosing an
appropriate combination of the integrator and :doc:`pair_style dpd/fdt <pair_style>` command. DPD under isothermal conditions can
be specified by using fix *shardlow*, fix *nve* and pair_style
*dpd/fdt*. DPD under isoenergetic conditions can be specified by
using fix *shardlow*, fix *nve* and pair_style *dpd/fdt/energy*. DPD
under isobaric conditions can be specified by using fix shardlow, fix
*nph* and pair_style *dpd/fdt*. DPD under isoenthalpic conditions can
be specified by using fix shardlow, fix *nph* and pair_style
*dpd/fdt/energy*. Examples of each DPD variant are provided in the
examples/USER/dpd directory.
----------
Restrictions
""""""""""""
This fix is only available if LAMMPS is built with the USER-DPD
package. See the :ref:`Making LAMMPS <start_3>` section
for more info.
This fix is currently limited to orthogonal simulation cell
geometries.
This fix must be used with an additional fix that specifies time
integration, e.g. :doc:`fix nve <fix_nve>` or :doc:`fix nph <fix_nh>`.
The Shardlow splitting algorithm requires the sizes of the sub-domain
lengths to be larger than twice the cutoff+skin. Generally, the
domain decomposition is dependant on the number of processors
requested.
Related commands
""""""""""""""""
:doc:`pair_style dpd/fdt <pair_dpd_fdt>`, :doc:`fix eos/cv <fix_eos_cv>`
**Default:** none
----------
.. _Lisal:
**(Lisal)** M. Lisal, J.K. Brennan, J. Bonet Avalos, "Dissipative
particle dynamics as isothermal, isobaric, isoenergetic, and
isoenthalpic conditions using Shardlow-like splitting algorithms.",
J. Chem. Phys., 135, 204105 (2011).
.. _Larentzos:
**(Larentzos)** J.P. Larentzos, J.K. Brennan, J.D. Moore, M. Lisal and
W.D. Mattson, "Parallel Implementation of Isothermal and Isoenergetic
Dissipative Particle Dynamics Using Shardlow-Like Splitting
Algorithms", Comput. Phys. Commun., 185, 1987-1998 (2014).
.. _Larentzos:
**(Larentzos)** J.P. Larentzos, J.K. Brennan, J.D. Moore, and
W.D. Mattson, "LAMMPS Implementation of Constant Energy Dissipative
Particle Dynamics (DPD-E)", ARL-TR-6863, U.S. Army Research
Laboratory, Aberdeen Proving Ground, MD (2014).
.. _lws: http://lammps.sandia.gov
.. _ld: Manual.html
.. _lc: Section_commands.html#comm
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