152 lines
5.0 KiB
ReStructuredText
152 lines
5.0 KiB
ReStructuredText
.. index:: pair_style lambda/input/apip
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.. index:: pair_style lambda/input/csp/apip
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pair_style lambda/input/apip 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 lambda/input/apip cutoff
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* lambda/input/apip = style name of this pair style
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* cutoff = global cutoff (distance units)
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pair_style lambda/input/csp/apip 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 lambda/input/csp/apip lattice keyword args
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* lambda/input/csp/apip = style name of this pair style
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* lattice = *fcc* or *bcc* or integer
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.. parsed-literal::
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*fcc* = use 12 nearest neighbors to calculate the CSP like in a perfect fcc lattice
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*bcc* = use 8 nearest neighbors to calculate the CSP like in a perfect bcc lattice
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integer = use N nearest neighbors to calculate the CSP
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* zero or more keyword/args pairs may be appended
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* keyword = *cutoff* or *N_buffer*
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.. parsed-literal::
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*cutoff* args = cutoff
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cutoff = distance in which neighboring atoms are considered (> 0)
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*N_buffer* args = N_buffer
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N_buffer = number of additional neighbors, which are included in the j-j+N/2 calculation
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Examples
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""""""""
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.. code-block:: LAMMPS
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pair_style lambda/input/csp/apip fcc
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pair_style lambda/input/csp/apip fcc cutoff 5.0
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pair_style lambda/input/csp/apip bcc cutoff 5.0 N_buffer 2
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pair_style lambda/input/csp/apip 14
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Description
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"""""""""""
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This pair_styles calculates :math:`\lambda_i^\text{input}(t)`, which
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is required for :doc:`fix lambda/apip <fix_lambda_apip>`.
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The pair_style lambda_input sets :math:`\lambda_i^\text{input}(t) = 0`.
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The pair_style lambda_input/csp calculates
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:math:`\lambda_i^\text{input}(t) = \text{CSP}_i(t)`.
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The centro-symmetry parameter (CSP) :ref:`(Kelchner) <Kelchner_2>` is described
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in :doc:`compute centro/atom <compute_centro_atom>`.
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The lattice argument is described in
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:doc:`compute centro/atom <compute_centro_atom>` and determines
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the number of neighboring atoms that are used to compute the CSP.
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The *N_buffer* argument allows to include more neighboring atoms in
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the calculation of the contributions from the pair j,j+N/2 to the CSP as
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discussed in :ref:`(Immel) <Immel2025_6>`.
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The computation of :math:`\lambda_i^\text{input}(t)` is done by this
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pair_style instead of by :doc:`fix lambda/apip <fix_lambda_apip>`, as this computation
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takes time and this pair_style can be included in the load-balancing via
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:doc:`fix atom_weight/apip <fix_atom_weight_apip>`.
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A code example for the calculation of the switching parameter for an adaptive-
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precision potential is given in the following:
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The adaptive-precision potential is created
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by combining :doc:`pair_style eam/fs/apip <pair_eam_apip>`
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and :doc:`pair_style pace/precise/apip <pair_pace_apip>`.
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The input, from which the switching parameter is calculated, is provided
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by this pair_style.
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The switching parameter is calculated by :doc:`fix lambda/apip <fix_lambda_apip>`,
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whereas the spatial
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transition zone of the switching parameter is calculated by
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:doc:`pair_style lambda/zone/apip <pair_lambda_zone_apip>`.
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.. code-block:: LAMMPS
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pair_style hybrid/overlay eam/fs/apip pace/precise/apip lambda/input/csp/apip fcc cutoff 5.0 lambda/zone/apip 12.0
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pair_coeff * * eam/fs/apip Cu.eam.fs Cu
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pair_coeff * * pace/precise/apip Cu_precise.yace Cu
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pair_coeff * * lambda/input/csp/apip
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pair_coeff * * lambda/zone/apip
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fix 2 all lambda/apip 3.0 3.5 time_averaged_zone 4.0 12.0 110 110 min_delta_lambda 0.01
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----------
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Mixing, shift, table, tail correction, restart, rRESPA info
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"""""""""""""""""""""""""""""""""""""""""""""""""""""""""""
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The cutoff distance for this pair style can be mixed. The default mix
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value is *geometric*\ . See the "pair_modify" command for details.
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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 writes no information to :doc:`binary restart files <restart>`, so pair_style and pair_coeff commands need
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to be specified in an input script that reads a restart file.
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This pair style does not support the use of the *inner*, *middle*,
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and *outer* keywords of the :doc:`run_style respa <run_style>` command.
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----------
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Restrictions
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""""""""""""
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This fix is part of the APIP package. It is only enabled if
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LAMMPS was built with that package. See the :doc:`Build package
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<Build_package>` page for more info.
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Related commands
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""""""""""""""""
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:doc:`compute centro/atom <compute_centro_atom>`,
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:doc:`fix lambda/apip <fix_lambda_apip>`,
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:doc:`fix lambda_thermostat/apip <fix_lambda_thermostat_apip>`,
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:doc:`pair_style lambda/zone/apip <pair_lambda_zone_apip>`,
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:doc:`pair_style eam/apip <pair_eam_apip>`,
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:doc:`pair_style pace/apip <pair_pace_apip>`,
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:doc:`fix atom_weight/apip <fix_atom_weight_apip>`
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Default
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"""""""
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N_buffer=0, cutoff=5.0
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----------
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.. _Kelchner_2:
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**(Kelchner)** Kelchner, Plimpton, Hamilton, Phys Rev B, 58, 11085 (1998).
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.. _Immel2025_6:
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**(Immel)** Immel, Drautz and Sutmann, J Chem Phys, 162, 114119 (2025)
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