91 lines
2.4 KiB
ReStructuredText
91 lines
2.4 KiB
ReStructuredText
.. index:: compute dpd
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compute dpd command
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===================
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Syntax
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""""""
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.. code-block:: LAMMPS
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compute ID group-ID dpd
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* ID, group-ID are documented in :doc:`compute <compute>` command
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* dpd = style name of this compute command
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Examples
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""""""""
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.. code-block:: LAMMPS
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compute 1 all dpd
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Description
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"""""""""""
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Define a computation that accumulates the total internal conductive
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energy (:math:`U^{\text{cond}}`), the total internal mechanical energy
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(:math:`U^{\text{mech}}`), the total chemical energy (:math:`U^\text{chem}`)
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and the *harmonic* average of the internal temperature (:math:`\theta_\text{avg}`)
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for the entire system of particles. See the
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:doc:`compute dpd/atom <compute_dpd_atom>` command if you want
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per-particle internal energies and internal temperatures.
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The system internal properties are computed according to the following
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relations:
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.. math::
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U^\text{cond} = & \sum_{i=1}^{N} u_{i}^\text{cond} \\
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U^\text{mech} = & \sum_{i=1}^{N} u_{i}^\text{mech} \\
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U^\text{chem} = & \sum_{i=1}^{N} u_{i}^\text{chem} \\
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U = & \sum_{i=1}^{N} (u_{i}^\text{cond}
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+ u_{i}^\text{mech} + u_{i}^\text{chem}) \\
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\theta_{avg} = & \biggl(\frac{1}{N}\sum_{i=1}^{N}
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\frac{1}{\theta_{i}}\biggr)^{-1} \\
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where :math:`N` is the number of particles in the system.
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----------
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Output info
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"""""""""""
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This compute calculates a global vector of length 5 (:math:`U^\text{cond}`,
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:math:`U^\text{mech}`, :math:`U^\text{chem}`, :math:`\theta_\text{avg}`,
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:math:`N`), which can be accessed by indices 1 through 5.
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See the :doc:`Howto output <Howto_output>` page for an overview of
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LAMMPS output options.
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The vector values will be in energy and temperature :doc:`units <units>`.
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Restrictions
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""""""""""""
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This command is part of the DPD-REACT package. It is only enabled if
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LAMMPS was built with that package.
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See the :doc:`Build package <Build_package>` page for more info.
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This command also requires use of the :doc:`atom_style dpd <atom_style>`
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command.
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Related commands
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""""""""""""""""
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:doc:`compute dpd/atom <compute_dpd_atom>`,
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:doc:`thermo_style <thermo_style>`
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Default
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"""""""
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none
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----------
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.. _Larentzos1:
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**(Larentzos)** J.P. Larentzos, J.K. Brennan, J.D. Moore, and
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W.D. Mattson, "LAMMPS Implementation of Constant Energy Dissipative
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Particle Dynamics (DPD-E)", ARL-TR-6863, U.S. Army Research
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Laboratory, Aberdeen Proving Ground, MD (2014).
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