forked from lijiext/lammps
140 lines
4.1 KiB
ReStructuredText
140 lines
4.1 KiB
ReStructuredText
.. index:: pair_style gw
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pair_style gw command
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=====================
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pair_style gw/zbl 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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pair_style style
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* style = *gw* or *gw/zbl*
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Examples
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""""""""
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.. code-block:: LAMMPS
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pair_style gw
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pair_coeff * * SiC.gw Si C C
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pair_style gw/zbl
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pair_coeff * * SiC.gw.zbl C Si
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Description
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"""""""""""
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The *gw* style computes a 3-body :ref:`Gao-Weber <Gao>` potential;
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similarly *gw/zbl* combines this potential with a modified
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repulsive ZBL core function in a similar fashion as implemented
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in the :doc:`tersoff/zbl <pair_tersoff_zbl>` pair style.
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Unfortunately the author of this contributed code has not been
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able to submit a suitable documentation explaining the details
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of the potentials. The LAMMPS developers thus have finally decided
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to release the code anyway with only the technical explanations.
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For details of the model and the parameters, please refer to the
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linked publication.
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Only a single pair\_coeff command is used with the *gw* and *gw/zbl*
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styles which specifies a Gao-Weber potential file with parameters
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for all needed elements. These are mapped to LAMMPS atom types by
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specifying N additional arguments after the filename in the pair\_coeff
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command, where N is the number of LAMMPS atom types:
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* filename
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* N element names = mapping of GW elements to atom types
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See the :doc:`pair_coeff <pair_coeff>` doc page for alternate ways
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to specify the path for the potential file.
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As an example, imagine a file SiC.gw has Gao-Weber values for Si and C.
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If your LAMMPS simulation has 4 atoms types and you want the first 3 to
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be Si, and the 4th to be C, you would use the following pair\_coeff command:
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.. code-block:: LAMMPS
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pair_coeff * * SiC.gw Si Si Si C
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The first 2 arguments must be \* \* so as to span all LAMMPS atom types.
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The first three Si arguments map LAMMPS atom types 1,2,3 to the Si
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element in the GW file. The final C argument maps LAMMPS atom type 4
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to the C element in the GW file. If a mapping value is specified as
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NULL, the mapping is not performed. This can be used when a *gw*
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potential is used as part of the *hybrid* pair style. The NULL values
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are placeholders for atom types that will be used with other
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potentials.
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Gao-Weber files in the *potentials* directory of the LAMMPS
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distribution have a ".gw" suffix. Gao-Weber with ZBL files
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have a ".gz.zbl" suffix. The structure of the potential files
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is similar to other many-body potentials supported by LAMMPS.
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You have to refer to the comments in the files and the literature
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to learn more details.
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----------
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**Mixing, shift, table, tail correction, restart, rRESPA info**\ :
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For atom type pairs I,J and I != J, where types I and J correspond to
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two different element types, mixing is performed by LAMMPS as
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described above from values in the potential file.
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This pair style does not support the :doc:`pair_modify <pair_modify>`
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shift, table, and tail options.
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This pair style does not write its information to :doc:`binary restart files <restart>`, since it is stored in potential files. Thus, you
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need to re-specify the pair\_style and pair\_coeff commands in an input
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script that reads a restart file.
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This pair style can only be used via the *pair* keyword of the
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:doc:`run_style respa <run_style>` command. It does not support the
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*inner*\ , *middle*\ , *outer* keywords.
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----------
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Restrictions
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""""""""""""
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This pair style is part of the MANYBODY package. It is only enabled if
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LAMMPS was built with that package. See the :doc:`Build package <Build_package>` doc page for more info.
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This pair style requires the :doc:`newton <newton>` setting to be "on"
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for pair interactions.
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The Gao-Weber potential files provided with LAMMPS (see the
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potentials directory) are parameterized for metal :doc:`units <units>`.
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You can use the GW potential with any LAMMPS units, but you would need
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to create your own GW potential file with coefficients listed in the
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appropriate units if your simulation doesn't use "metal" units.
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Related commands
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""""""""""""""""
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:doc:`pair_coeff <pair_coeff>`
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**Default:** none
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----------
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.. _Gao:
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**(Gao)** Gao and Weber, Nuclear Instruments and Methods in Physics
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Research B 191 (2012) 504.
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