forked from lijiext/lammps
204 lines
6.5 KiB
Plaintext
204 lines
6.5 KiB
Plaintext
.. index:: pair_style nm/cut
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pair_style nm/cut command
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=========================
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pair_style nm/cut/coul/cut command
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==================================
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pair_style nm/cut/coul/long command
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===================================
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pair_style nm/cut/omp command
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=============================
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pair_style nm/cut/coul/cut/omp command
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======================================
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pair_style nm/cut/coul/long/omp command
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=======================================
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Syntax
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""""""
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.. parsed-literal::
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pair_style style args
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* style = *nm/cut* or *nm/cut/coul/cut* or *nm/cut/coul/long*
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* args = list of arguments for a particular style
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.. parsed-literal::
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*nm/cut* args = cutoff
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cutoff = global cutoff for Pair interactions (distance units)
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*nm/cut/coul/cut* args = cutoff (cutoff2)
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cutoff = global cutoff for Pair (and Coulombic if only 1 arg) (distance units)
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cutoff2 = global cutoff for Coulombic (optional) (distance units)
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*nm/cut/coul/long* args = cutoff (cutoff2)
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cutoff = global cutoff for Pair (and Coulombic if only 1 arg) (distance units)
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cutoff2 = global cutoff for Coulombic (optional) (distance units)
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Examples
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""""""""
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.. parsed-literal::
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pair_style nm/cut 12.0
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pair_coeff * * 0.01 5.4 8.0 7.0
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pair_coeff 1 1 0.01 4.4 7.0 6.0
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.. parsed-literal::
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pair_style nm/cut/coul/cut 12.0 15.0
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pair_coeff * * 0.01 5.4 8.0 7.0
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pair_coeff 1 1 0.01 4.4 7.0 6.0
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.. parsed-literal::
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pair_style nm/cut/coul/long 12.0 15.0
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pair_coeff * * 0.01 5.4 8.0 7.0
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pair_coeff 1 1 0.01 4.4 7.0 6.0
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Description
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"""""""""""
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Style *nm* computes site-site interactions based on the N-M potential
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by :ref:`Clarke <Clarke>`, mainly used for ionic liquids. A site can
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represent a single atom or a united-atom site. The energy of an
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interaction has the following form:
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.. image:: Eqs/pair_nm.jpg
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:align: center
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Rc is the cutoff.
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Style *nm/cut/coul/cut* adds a Coulombic pairwise interaction given by
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.. image:: Eqs/pair_coulomb.jpg
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:align: center
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where C is an energy-conversion constant, Qi and Qj are the charges on
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the 2 atoms, and epsilon is the dielectric constant which can be set
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by the :doc:`dielectric <dielectric>` command. If one cutoff is
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specified in the pair_style command, it is used for both the NM and
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Coulombic terms. If two cutoffs are specified, they are used as
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cutoffs for the NM and Coulombic terms respectively.
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Styles *nm/cut/coul/long* compute the same
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Coulombic interactions as style *nm/cut/coul/cut* except that an
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additional damping factor is applied to the Coulombic term so it can
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be used in conjunction with the :doc:`kspace_style <kspace_style>`
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command and its *ewald* or *pppm* option. The Coulombic cutoff
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specified for this style means that pairwise interactions within this
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distance are computed directly; interactions outside that distance are
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computed in reciprocal space.
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For all of the *nm* pair styles, the following coefficients must
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be defined for each pair of atoms types
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via the :doc:`pair_coeff <pair_coeff>` command as in the
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examples above, or in the data file or restart files read by the
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:doc:`read_data <read_data>` or :doc:`read_restart <read_restart>`
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commands.
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* E0 (energy units)
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* r0 (distance units)
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* n (unitless)
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* m (unitless)
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* cutoff1 (distance units)
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* cutoff2 (distance units)
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The latter 2 coefficients are optional. If not specified, the global
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NM and Coulombic cutoffs specified in the pair_style command are used.
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If only one cutoff is specified, it is used as the cutoff for both NM
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and Coulombic interactions for this type pair. If both coefficients
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are specified, they are used as the NM and Coulombic cutoffs for this
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type pair. You cannot specify 2 cutoffs for style *nm*\ , since it
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has no Coulombic terms.
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For *nm/cut/coul/long* only the NM cutoff can be specified since a
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Coulombic cutoff cannot be specified for an individual I,J type pair.
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All type pairs use the same global Coulombic cutoff specified in the
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pair_style command.
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----------
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**Mixing, shift, table, tail correction, restart, rRESPA info**\ :
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These pair styles do not support mixing. Thus, coefficients for all
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I,J pairs must be specified explicitly.
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All of the *nm* pair styles supports the
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:doc:`pair_modify <pair_modify>` shift option for the energy of the pair
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interaction.
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The *nm/cut/coul/long* pair styles support the
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:doc:`pair_modify <pair_modify>` table option since they can tabulate
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the short-range portion of the long-range Coulombic interaction.
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All of the *nm* pair styles support the :doc:`pair_modify <pair_modify>`
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tail option for adding a long-range tail correction to the energy and
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pressure for the NM portion of the pair interaction.
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All of the *nm* pair styles write their information to :doc:`binary restart files <restart>`, so pair_style and pair_coeff commands do not need
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to be specified in an input script that reads a restart file.
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All of the *nm* pair styles can only be used via the *pair* keyword of
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the :doc:`run_style respa <run_style>` command. They do not support the
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*inner*\ , *middle*\ , *outer* keywords.
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----------
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Styles with a *gpu*\ , *intel*\ , *kk*\ , *omp*\ , or *opt* suffix are
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functionally the same as the corresponding style without the suffix.
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They have been optimized to run faster, depending on your available
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hardware, as discussed in :doc:`Section_accelerate <Section_accelerate>`
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of the manual. The accelerated styles take the same arguments and
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should produce the same results, except for round-off and precision
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issues.
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These accelerated styles are part of the GPU, USER-INTEL, KOKKOS,
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USER-OMP and OPT packages, respectively. They are only enabled if
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LAMMPS was built with those packages. See the :ref:`Making LAMMPS <start_3>` section for more info.
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You can specify the accelerated styles explicitly in your input script
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by including their suffix, or you can use the :ref:`-suffix command-line switch <start_7>` when you invoke LAMMPS, or you can
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use the :doc:`suffix <suffix>` command in your input script.
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See :doc:`Section_accelerate <Section_accelerate>` of the manual for
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more instructions on how to use the accelerated styles effectively.
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Restrictions
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""""""""""""
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These pair styles are part of the MISC 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:`pair_coeff <pair_coeff>`
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**Default:** none
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----------
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.. _Clarke:
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**(Clarke)** Clarke and Smith, J Chem Phys, 84, 2290 (1986).
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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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