forked from lijiext/lammps
72 lines
2.0 KiB
Plaintext
72 lines
2.0 KiB
Plaintext
.. index:: compute dilatation/atom
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compute dilatation/atom command
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===============================
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Syntax
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""""""
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.. parsed-literal::
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compute ID group-ID dilatation/atom
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* ID, group-ID are documented in compute command
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* dilation/atom = style name of this compute command
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Examples
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""""""""
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.. parsed-literal::
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compute 1 all dilatation/atom
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Description
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"""""""""""
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Define a computation that calculates the per-atom dilatation for each
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atom in a group. This is a quantity relevant for :doc:`Peridynamics models <pair_peri>`. See `this document <PDF/PDLammps_overview.pdf>`_
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for an overview of LAMMPS commands for Peridynamics modeling.
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For small deformation, dilatation of is the measure of the volumetric
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strain.
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The dilatation "theta" for each peridynamic particle I is calculated
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as a sum over its neighbors with unbroken bonds, where the
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contribution of the IJ pair is a function of the change in bond length
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(versus the initial length in the reference state), the volume
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fraction of the particles and an influence function. See the
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`PDLAMMPS user guide <http://www.sandia.gov/~mlparks/papers/PDLAMMPS.pdf>`_ for a formal
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definition of dilatation.
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This command can only be used with a subset of the Peridynamic :doc:`pair styles <pair_peri>`: peri/lps, peri/ves and peri/eps.
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The dilatation value will be 0.0 for atoms not in the specified
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compute group.
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**Output info:**
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This compute calculates a per-atom vector, which can be accessed by
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any command that uses per-atom values from a compute as input. See
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Section_howto 15 for an overview of LAMMPS output options.
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The per-atom vector values are unitlesss numbers (theta) >= 0.0.
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Restrictions
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""""""""""""
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This compute is part of the PERI package. It is only enabled if
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LAMMPS was built with that package. See the :ref:`Making LAMMPS <start_3>` section for more info.
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Related commands
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""""""""""""""""
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:doc:`compute damage <compute_damage>`, :doc:`compute plasticity <compute_plasticity>`
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**Default:** none
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.. _lws: http://lammps.sandia.gov
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.. _ld: Manual.html
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.. _lc: Section_commands.html#comm
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