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.. index:: pair_style
pair_style command
==================
Syntax
""""""
.. parsed-literal::
pair_style style args
* style = one of the styles from the list below
* args = arguments used by a particular style
Examples
""""""""
.. parsed-literal::
pair_style lj/cut 2.5
pair_style eam/alloy
pair_style hybrid lj/charmm/coul/long 10.0 eam
pair_style table linear 1000
pair_style none
Description
"""""""""""
Set the formula(s) LAMMPS uses to compute pairwise interactions. In
LAMMPS, pair potentials are defined between pairs of atoms that are
within a cutoff distance and the set of active interactions typically
changes over time. See the :doc:`bond_style <bond_style>` command to
define potentials between pairs of bonded atoms, which typically
remain in place for the duration of a simulation.
In LAMMPS, pairwise force fields encompass a variety of interactions,
some of which include many-body effects, e.g. EAM, Stillinger-Weber,
Tersoff, REBO potentials. They are still classified as "pairwise"
potentials because the set of interacting atoms changes with time
(unlike molecular bonds) and thus a neighbor list is used to find
nearby interacting atoms.
Hybrid models where specified pairs of atom types interact via
different pair potentials can be setup using the *hybrid* pair style.
The coefficients associated with a pair style are typically set for
each pair of atom types, and are specified by the
:doc:`pair_coeff <pair_coeff>` command or read from a file by the
:doc:`read_data <read_data>` or :doc:`read_restart <read_restart>`
commands.
The :doc:`pair_modify <pair_modify>` command sets options for mixing of
type I-J interaction coefficients and adding energy offsets or tail
corrections to Lennard-Jones potentials. Details on these options as
they pertain to individual potentials are described on the doc page
for the potential. Likewise, info on whether the potential
information is stored in a :doc:`restart file <write_restart>` is listed
on the potential doc page.
In the formulas listed for each pair style, *E* is the energy of a
pairwise interaction between two atoms separated by a distance *r*.
The force between the atoms is the negative derivative of this
expression.
If the pair_style command has a cutoff argument, it sets global
cutoffs for all pairs of atom types. The distance(s) can be smaller
or larger than the dimensions of the simulation box.
Typically, the global cutoff value can be overridden for a specific
pair of atom types by the :doc:`pair_coeff <pair_coeff>` command. The
pair style settings (including global cutoffs) can be changed by a
subsequent pair_style command using the same style. This will reset
the cutoffs for all atom type pairs, including those previously set
explicitly by a :doc:`pair_coeff <pair_coeff>` command. The exceptions
to this are that pair_style *table* and *hybrid* settings cannot be
reset. A new pair_style command for these styles will wipe out all
previously specified pair_coeff values.
----------
Here is an alphabetic list of pair styles defined in LAMMPS. They are
also given in more compact form in the pair section of :ref:`this page <cmd_5>`.
Click on the style to display the formula it computes, arguments
specified in the pair_style command, and coefficients specified by the
associated :doc:`pair_coeff <pair_coeff>` command.
There are also additional pair styles (not listed here) submitted by
users which are included in the LAMMPS distribution. The list of
these with links to the individual styles are given in the pair
section of :ref:`this page <cmd_5>`.
There are also additional accelerated pair styles (not listed here)
included in the LAMMPS distribution for faster performance on CPUs and
GPUs. The list of these with links to the individual styles are given
in the pair section of :ref:`this page <cmd_5>`.
* :doc:`pair_style none <pair_none>` - turn off pairwise interactions
* :doc:`pair_style hybrid <pair_hybrid>` - multiple styles of pairwise interactions
* :doc:`pair_style hybrid/overlay <pair_hybrid>` - multiple styles of superposed pairwise interactions
* :doc:`pair_style adp <pair_adp>` - angular dependent potential (ADP) of Mishin
* :doc:`pair_style airebo <pair_airebo>` - AIREBO potential of Stuart
* :doc:`pair_style beck <pair_beck>` - Beck potential
* :doc:`pair_style body <pair_body>` - interactions between body particles
* :doc:`pair_style bop <pair_bop>` - BOP potential of Pettifor
* :doc:`pair_style born <pair_born>` - Born-Mayer-Huggins potential
* :doc:`pair_style born/coul/long <pair_born>` - Born-Mayer-Huggins with long-range Coulombics
* :doc:`pair_style born/coul/long/cs <pair_born>` - Born-Mayer-Huggins with long-range Coulombics and core/shell
* :doc:`pair_style born/coul/msm <pair_born>` - Born-Mayer-Huggins with long-range MSM Coulombics
* :doc:`pair_style born/coul/wolf <pair_born>` - Born-Mayer-Huggins with Coulombics via Wolf potential
* :doc:`pair_style brownian <pair_brownian>` - Brownian potential for Fast Lubrication Dynamics
* :doc:`pair_style brownian/poly <pair_brownian>` - Brownian potential for Fast Lubrication Dynamics with polydispersity
* :doc:`pair_style buck <pair_buck>` - Buckingham potential
* :doc:`pair_style buck/coul/cut <pair_buck>` - Buckingham with cutoff Coulomb
* :doc:`pair_style buck/coul/long <pair_buck>` - Buckingham with long-range Coulombics
* :doc:`pair_style buck/coul/long/cs <pair_buck>` - Buckingham with long-range Coulombics and core/shell
* :doc:`pair_style buck/coul/msm <pair_buck>` - Buckingham long-range MSM Coulombics
* :doc:`pair_style buck/long/coul/long <pair_buck_long>` - long-range Buckingham with long-range Coulombics
* :doc:`pair_style colloid <pair_colloid>` - integrated colloidal potential
* :doc:`pair_style comb <pair_comb>` - charge-optimized many-body (COMB) potential
* :doc:`pair_style comb3 <pair_comb>` - charge-optimized many-body (COMB3) potential
* :doc:`pair_style coul/cut <pair_coul>` - cutoff Coulombic potential
* :doc:`pair_style coul/debye <pair_coul>` - cutoff Coulombic potential with Debye screening
* :doc:`pair_style coul/dsf <pair_coul>` - Coulombics via damped shifted forces
* :doc:`pair_style coul/long <pair_coul>` - long-range Coulombic potential
* :doc:`pair_style coul/long/cs <pair_coul>` - long-range Coulombic potential and core/shell
* :doc:`pair_style coul/msm <pair_coul>` - long-range MSM Coulombics
* :doc:`pair_style coul/msm <pair_coul_streitz>` - Coulombics via Streitz/Mintmire Slater orbitals
* :doc:`pair_style coul/wolf <pair_coul>` - Coulombics via Wolf potential
* :doc:`pair_style dpd <pair_dpd>` - dissipative particle dynamics (DPD)
* :doc:`pair_style dpd/tstat <pair_dpd>` - DPD thermostatting
* :doc:`pair_style dsmc <pair_dsmc>` - Direct Simulation Monte Carlo (DSMC)
* :doc:`pair_style eam <pair_eam>` - embedded atom method (EAM)
* :doc:`pair_style eam/alloy <pair_eam>` - alloy EAM
* :doc:`pair_style eam/fs <pair_eam>` - Finnis-Sinclair EAM
* :doc:`pair_style eim <pair_eim>` - embedded ion method (EIM)
* :doc:`pair_style gauss <pair_gauss>` - Gaussian potential
* :doc:`pair_style gayberne <pair_gayberne>` - Gay-Berne ellipsoidal potential
* :doc:`pair_style gran/hertz/history <pair_gran>` - granular potential with Hertzian interactions
* :doc:`pair_style gran/hooke <pair_gran>` - granular potential with history effects
* :doc:`pair_style gran/hooke/history <pair_gran>` - granular potential without history effects
* :doc:`pair_style hbond/dreiding/lj <pair_hbond_dreiding>` - DREIDING hydrogen bonding LJ potential
* :doc:`pair_style hbond/dreiding/morse <pair_hbond_dreiding>` - DREIDING hydrogen bonding Morse potential
* :doc:`pair_style kim <pair_kim>` - interface to potentials provided by KIM project
* :doc:`pair_style lcbop <pair_lcbop>` - long-range bond-order potential (LCBOP)
* :doc:`pair_style line/lj <pair_line_lj>` - LJ potential between line segments
* :doc:`pair_style lj/charmm/coul/charmm <pair_charmm>` - CHARMM potential with cutoff Coulomb
* :doc:`pair_style lj/charmm/coul/charmm/implicit <pair_charmm>` - CHARMM for implicit solvent
* :doc:`pair_style lj/charmm/coul/long <pair_charmm>` - CHARMM with long-range Coulomb
* :doc:`pair_style lj/charmm/coul/msm <pair_charmm>` - CHARMM with long-range MSM Coulombics
* :doc:`pair_style lj/class2 <pair_class2>` - COMPASS (class 2) force field with no Coulomb
* :doc:`pair_style lj/class2/coul/cut <pair_class2>` - COMPASS with cutoff Coulomb
* :doc:`pair_style lj/class2/coul/long <pair_class2>` - COMPASS with long-range Coulomb
* :doc:`pair_style lj/cut <pair_lj>` - cutoff Lennard-Jones potential with no Coulomb
* :doc:`pair_style lj/cut/coul/cut <pair_lj>` - LJ with cutoff Coulomb
* :doc:`pair_style lj/cut/coul/debye <pair_lj>` - LJ with Debye screening added to Coulomb
* :doc:`pair_style lj/cut/coul/dsf <pair_lj>` - LJ with Coulombics via damped shifted forces
* :doc:`pair_style lj/cut/coul/long <pair_lj>` - LJ with long-range Coulombics
* :doc:`pair_style lj/cut/coul/msm <pair_lj>` - LJ with long-range MSM Coulombics
* :doc:`pair_style lj/cut/dipole/cut <pair_dipole>` - point dipoles with cutoff
* :doc:`pair_style lj/cut/dipole/long <pair_dipole>` - point dipoles with long-range Ewald
* :doc:`pair_style lj/cut/tip4p/cut <pair_lj>` - LJ with cutoff Coulomb for TIP4P water
* :doc:`pair_style lj/cut/tip4p/long <pair_lj>` - LJ with long-range Coulomb for TIP4P water
* :doc:`pair_style lj/expand <pair_lj_expand>` - Lennard-Jones for variable size particles
* :doc:`pair_style lj/gromacs <pair_gromacs>` - GROMACS-style Lennard-Jones potential
* :doc:`pair_style lj/gromacs/coul/gromacs <pair_gromacs>` - GROMACS-style LJ and Coulombic potential
* :doc:`pair_style lj/long/coul/long <pair_lj_long>` - long-range LJ and long-range Coulombics
* :doc:`pair_style lj/long/dipole/long <pair_dipole>` - long-range LJ and long-range point dipoles
* :doc:`pair_style lj/long/tip4p/long <pair_lj_long>` - long-range LJ and long-range Coulomb for TIP4P water
* :doc:`pair_style lj/smooth <pair_lj_smooth>` - smoothed Lennard-Jones potential
* :doc:`pair_style lj/smooth/linear <pair_lj_smooth_linear>` - linear smoothed Lennard-Jones potential
* :doc:`pair_style lj96/cut <pair_lj96>` - Lennard-Jones 9/6 potential
* :doc:`pair_style lubricate <pair_lubricate>` - hydrodynamic lubrication forces
* :doc:`pair_style lubricate/poly <pair_lubricate>` - hydrodynamic lubrication forces with polydispersity
* :doc:`pair_style lubricateU <pair_lubricateU>` - hydrodynamic lubrication forces for Fast Lubrication Dynamics
* :doc:`pair_style lubricateU/poly <pair_lubricateU>` - hydrodynamic lubrication forces for Fast Lubrication with polydispersity
* :doc:`pair_style meam <pair_meam>` - modified embedded atom method (MEAM)
* :doc:`pair_style mie/cut <pair_mie>` - Mie potential
* :doc:`pair_style morse <pair_morse>` - Morse potential
* :doc:`pair_style nb3b/harmonic <pair_nb3b_harmonic>` - nonbonded 3-body harmonic potential
* :doc:`pair_style nm/cut <pair_nm>` - N-M potential
* :doc:`pair_style nm/cut/coul/cut <pair_nm>` - N-M potential with cutoff Coulomb
* :doc:`pair_style nm/cut/coul/long <pair_nm>` - N-M potential with long-range Coulombics
* :doc:`pair_style peri/eps <pair_peri>` - peridynamic EPS potential
* :doc:`pair_style peri/lps <pair_peri>` - peridynamic LPS potential
* :doc:`pair_style peri/pmb <pair_peri>` - peridynamic PMB potential
* :doc:`pair_style peri/ves <pair_peri>` - peridynamic VES potential
* :doc:`pair_style polymorphic <pair_polymorphic>` - polymorphic 3-body potential
* :doc:`pair_style reax <pair_reax>` - ReaxFF potential
* :doc:`pair_style rebo <pair_airebo>` - 2nd generation REBO potential of Brenner
* :doc:`pair_style resquared <pair_resquared>` - Everaers RE-Squared ellipsoidal potential
* :doc:`pair_style snap <pair_snap>` - SNAP quantum-accurate potential
* :doc:`pair_style soft <pair_soft>` - Soft (cosine) potential
* :doc:`pair_style sw <pair_sw>` - Stillinger-Weber 3-body potential
* :doc:`pair_style table <pair_table>` - tabulated pair potential
* :doc:`pair_style tersoff <pair_tersoff>` - Tersoff 3-body potential
* :doc:`pair_style tersoff/mod <pair_tersoff_mod>` - modified Tersoff 3-body potential
* :doc:`pair_style tersoff/zbl <pair_tersoff_zbl>` - Tersoff/ZBL 3-body potential
* :doc:`pair_style tip4p/cut <pair_coul>` - Coulomb for TIP4P water w/out LJ
* :doc:`pair_style tip4p/long <pair_coul>` - long-range Coulombics for TIP4P water w/out LJ
* :doc:`pair_style tri/lj <pair_tri_lj>` - LJ potential between triangles
* :doc:`pair_style vashishta <pair_vahishta>` - Vashishta 2-body and 3-body potential
* :doc:`pair_style yukawa <pair_yukawa>` - Yukawa potential
* :doc:`pair_style yukawa/colloid <pair_yukawa_colloid>` - screened Yukawa potential for finite-size particles
* :doc:`pair_style zbl <pair_zbl>` - Ziegler-Biersack-Littmark potential
----------
Restrictions
""""""""""""
This command must be used before any coefficients are set by the
:doc:`pair_coeff <pair_coeff>`, :doc:`read_data <read_data>`, or
:doc:`read_restart <read_restart>` commands.
Some pair styles are part of specific packages. They are only enabled
if LAMMPS was built with that package. See the :ref:`Making LAMMPS <start_3>` section for more info on packages.
The doc pages for individual pair potentials tell if it is part of a
package.
Related commands
""""""""""""""""
:doc:`pair_coeff <pair_coeff>`, :doc:`read_data <read_data>`,
:doc:`pair_modify <pair_modify>`, :doc:`kspace_style <kspace_style>`,
:doc:`dielectric <dielectric>`, :doc:`pair_write <pair_write>`
Default
"""""""
.. parsed-literal::
pair_style none
.. _lws: http://lammps.sandia.gov
.. _ld: Manual.html
.. _lc: Section_commands.html#comm
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