\(\renewcommand{\AA}{\text{Å}}\)
pair_style command
Syntax
pair_style style args
style = one of the styles from the list below
args = arguments used by a particular style
Examples
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 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 pair_coeff command or read from a file by the read_data or read_restart commands.
The 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 restart file 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.
In many cases, the global cutoff value can be overridden for a specific pair of atom types by the pair_coeff command.
If a new pair_style command is specified with a new style, all previous pair_coeff and pair_modify command settings are erased; those commands must be re-specified if necessary.
If a new pair_style command is specified with the same style, then only the global settings in that command are reset. Any previous doc:pair_coeff <pair_coeff> and pair_modify command settings are preserved. The only exception is that if the global cutoff in the pair_style command is changed, it will override the corresponding cutoff in any of the previous pair_modify commands.
Two pair styles which do not follow this rule are the pair_style table and hybrid commands. A new pair_style command for these styles will wipe out all previously specified pair_coeff and pair_modify settings, including for the sub-styles of the hybrid command.
Here is an alphabetic list of pair styles defined in LAMMPS. They are also listed in more compact form on the Commands pair doc page.
Click on the style to display the formula it computes, any additional arguments specified in the pair_style command, and coefficients specified by the associated pair_coeff command.
There are also additional accelerated pair styles included in the LAMMPS distribution for faster performance on CPUs, GPUs, and KNLs. The individual style names on the Commands pair doc page are followed by one or more of (g,i,k,o,t) to indicate which accelerated styles exist.
none - turn off pairwise interactions
hybrid - multiple styles of pairwise interactions
hybrid/molecular - different pair styles for intra- and inter-molecular interactions
hybrid/overlay - multiple styles of superposed pairwise interactions
hybrid/scaled - multiple styles of scaled superposed pairwise interactions
zero - neighbor list but no interactions
adp - angular dependent potential (ADP) of Mishin
agni - AGNI machine-learning potential
aip/water/2dm - anisotropic interfacial potential for water in 2d geometries
airebo - AIREBO potential of Stuart
airebo/morse - AIREBO with Morse instead of LJ
amoeba -
atm - Axilrod-Teller-Muto potential
awpmd/cut - Antisymmetrized Wave Packet MD potential for atoms and electrons
beck - Beck potential
body/nparticle - interactions between body particles
body/rounded/polygon - granular-style 2d polygon potential
body/rounded/polyhedron - granular-style 3d polyhedron potential
bop - BOP potential of Pettifor
born - Born-Mayer-Huggins potential
born/coul/dsf - Born with damped-shifted-force model
born/coul/dsf/cs - Born with damped-shifted-force and core/shell model
born/coul/long - Born with long-range Coulomb
born/coul/long/cs - Born with long-range Coulomb and core/shell
born/coul/msm - Born with long-range MSM Coulomb
born/coul/wolf - Born with Wolf potential for Coulomb
born/coul/wolf/cs - Born with Wolf potential for Coulomb and core/shell model
born/gauss - Born-Mayer / Gaussian potential
bpm/spring - repulsive harmonic force with damping
brownian - Brownian potential for Fast Lubrication Dynamics
brownian/poly - Brownian potential for Fast Lubrication Dynamics with polydispersity
buck - Buckingham potential
buck/coul/cut - Buckingham with cutoff Coulomb
buck/coul/long - Buckingham with long-range Coulomb
buck/coul/long/cs - Buckingham with long-range Coulomb and core/shell
buck/coul/msm - Buckingham with long-range MSM Coulomb
buck/long/coul/long - long-range Buckingham with long-range Coulomb
buck/mdf - Buckingham with a taper function
buck6d/coul/gauss/dsf - dispersion-damped Buckingham with damped-shift-force model
buck6d/coul/gauss/long - dispersion-damped Buckingham with long-range Coulomb
colloid - integrated colloidal potential
comb - charge-optimized many-body (COMB) potential
comb3 - charge-optimized many-body (COMB3) potential
cosine/squared - Cooke-Kremer-Deserno membrane model potential
coul/cut - cutoff Coulomb potential
coul/cut/global - cutoff Coulomb potential
coul/cut/soft - Coulomb potential with a soft core
coul/debye - cutoff Coulomb potential with Debye screening
coul/diel - Coulomb potential with dielectric permittivity
coul/dsf - Coulomb with damped-shifted-force model
coul/exclude - subtract Coulomb potential for excluded pairs
coul/long - long-range Coulomb potential
coul/long/cs - long-range Coulomb potential and core/shell
coul/long/soft - long-range Coulomb potential with a soft core
coul/msm - long-range MSM Coulomb
coul/slater/cut - smeared out Coulomb
coul/slater/long - long-range smeared out Coulomb
coul/shield - Coulomb for boron nitride for use with ilp/graphene/hbn potential
coul/streitz - Coulomb via Streitz/Mintmire Slater orbitals
coul/tt - damped charge-dipole Coulomb for Drude dipoles
coul/wolf - Coulomb via Wolf potential
coul/wolf/cs - Coulomb via Wolf potential with core/shell adjustments
dpd - dissipative particle dynamics (DPD)
dpd/coul/slater/long - dissipative particle dynamics (DPD) with electrostatic interactions
dpd/ext - generalized force field for DPD
dpd/ext/tstat - pairwise DPD thermostatting with generalized force field
dpd/fdt - DPD for constant temperature and pressure
dpd/fdt/energy - DPD for constant energy and enthalpy
dpd/tstat - pairwise DPD thermostatting
dsmc - Direct Simulation Monte Carlo (DSMC)
e3b - Explicit-three body (E3B) water model
drip - Dihedral-angle-corrected registry-dependent interlayer potential (DRIP)
eam - embedded atom method (EAM)
eam/alloy - alloy EAM
eam/cd - concentration-dependent EAM
eam/cd/old - older two-site model for concentration-dependent EAM
eam/fs - Finnis-Sinclair EAM
eam/he - Finnis-Sinclair EAM modified for Helium in metals
edip - three-body EDIP potential
edip/multi - multi-element EDIP potential
edpd - eDPD particle interactions
eff/cut - electron force field with a cutoff
eim - embedded ion method (EIM)
exp6/rx - reactive DPD potential
extep - extended Tersoff potential
gauss - Gaussian potential
gauss/cut - generalized Gaussian potential
gayberne - Gay-Berne ellipsoidal potential
granular - Generalized granular potential
gran/hertz/history - granular potential with Hertzian interactions
gran/hooke - granular potential with history effects
gran/hooke/history - granular potential without history effects
gw - Gao-Weber potential
gw/zbl - Gao-Weber potential with a repulsive ZBL core
harmonic/cut - repulsive-only harmonic potential
hbond/dreiding/lj - DREIDING hydrogen bonding LJ potential
hbond/dreiding/morse - DREIDING hydrogen bonding Morse potential
hdnnp - High-dimensional neural network potential
hippo -
ilp/graphene/hbn - registry-dependent interlayer potential (ILP)
ilp/tmd - interlayer potential (ILP) potential for transition metal dichalcogenides (TMD)
kim - interface to potentials provided by KIM project
kolmogorov/crespi/full - Kolmogorov-Crespi (KC) potential with no simplifications
kolmogorov/crespi/z - Kolmogorov-Crespi (KC) potential with normals along z-axis
lcbop - long-range bond-order potential (LCBOP)
lebedeva/z - Lebedeva interlayer potential for graphene with normals along z-axis
lennard/mdf - LJ potential in A/B form with a taper function
lepton - pair potential from evaluating a string
lepton/coul - pair potential from evaluating a string with support for charges
lepton/sphere - pair potential from evaluating a string with support for radii
line/lj - LJ potential between line segments
list - potential between pairs of atoms explicitly listed in an input file
lj/charmm/coul/charmm - CHARMM potential with cutoff Coulomb
lj/charmm/coul/charmm/implicit - CHARMM for implicit solvent
lj/charmm/coul/long - CHARMM with long-range Coulomb
lj/charmm/coul/long/soft - CHARMM with long-range Coulomb and a soft core
lj/charmm/coul/msm - CHARMM with long-range MSM Coulomb
lj/charmmfsw/coul/charmmfsh - CHARMM with force switching and shifting
lj/charmmfsw/coul/long - CHARMM with force switching and long-rnage Coulomb
lj/class2 - COMPASS (class 2) force field without Coulomb
lj/class2/coul/cut - COMPASS with cutoff Coulomb
lj/class2/coul/cut/soft - COMPASS with cutoff Coulomb with a soft core
lj/class2/coul/long - COMPASS with long-range Coulomb
lj/class2/coul/long/cs - COMPASS with long-range Coulomb with core/shell adjustments
lj/class2/coul/long/soft - COMPASS with long-range Coulomb with a soft core
lj/class2/soft - COMPASS (class 2) force field with no Coulomb with a soft core
lj/cubic - LJ with cubic after inflection point
lj/cut - cutoff Lennard-Jones potential without Coulomb
lj/cut/coul/cut - LJ with cutoff Coulomb
lj/cut/coul/cut/soft - LJ with cutoff Coulomb with a soft core
lj/cut/coul/debye - LJ with Debye screening added to Coulomb
lj/cut/coul/dsf - LJ with Coulomb via damped shifted forces
lj/cut/coul/long - LJ with long-range Coulomb
lj/cut/coul/long/cs - LJ with long-range Coulomb with core/shell adjustments
lj/cut/coul/long/soft - LJ with long-range Coulomb with a soft core
lj/cut/coul/msm - LJ with long-range MSM Coulomb
lj/cut/coul/wolf - LJ with Coulomb via Wolf potential
lj/cut/dipole/cut - point dipoles with cutoff
lj/cut/dipole/long - point dipoles with long-range Ewald
lj/cut/soft - LJ with a soft core
lj/cut/sphere - LJ where per-atom radius is used as LJ sigma
lj/cut/thole/long - LJ with Coulomb with thole damping
lj/cut/tip4p/cut - LJ with cutoff Coulomb for TIP4P water
lj/cut/tip4p/long - LJ with long-range Coulomb for TIP4P water
lj/cut/tip4p/long/soft - LJ with cutoff Coulomb for TIP4P water with a soft core
lj/expand - Lennard-Jones for variable size particles
lj/expand/coul/long - Lennard-Jones for variable size particles with long-range Coulomb
lj/expand/sphere - Variable size LJ where per-atom radius is used as delta (size)
lj/gromacs - GROMACS-style Lennard-Jones potential
lj/gromacs/coul/gromacs - GROMACS-style LJ and Coulomb potential
lj/long/coul/long - long-range LJ and long-range Coulomb
lj/long/dipole/long - long-range LJ and long-range point dipoles
lj/long/tip4p/long - long-range LJ and long-range Coulomb for TIP4P water
lj/mdf - LJ potential with a taper function
lj/relres - LJ using multiscale Relative Resolution (RelRes) methodology (Chaimovich).
lj/spica - LJ for SPICA coarse-graining
lj/spica/coul/long - LJ for SPICA coarse-graining with long-range Coulomb
lj/spica/coul/msm - LJ for SPICA coarse-graining with long-range Coulomb via MSM
lj/sf/dipole/sf - LJ with dipole interaction with shifted forces
lj/smooth - smoothed Lennard-Jones potential
lj/smooth/linear - linear smoothed LJ potential
lj/switch3/coulgauss/long - smoothed LJ vdW potential with Gaussian electrostatics
lj96/cut - Lennard-Jones 9/6 potential
local/density - Generalized basic local density potential
lubricate - Hydrodynamic lubrication forces
lubricate/poly - Hydrodynamic lubrication forces with polydispersity
lubricateU - Hydrodynamic lubrication forces for Fast Lubrication Dynamics
lubricateU/poly - Hydrodynamic lubrication forces for Fast Lubrication with polydispersity
mdpd - mDPD particle interactions
mdpd/rhosum - mDPD particle interactions for mass density
meam - Modified embedded atom method (MEAM)
meam/ms - Multi-state modified embedded atom method (MS-MEAM)
meam/spline - Splined version of MEAM
meam/sw/spline - Splined version of MEAM with a Stillinger-Weber term
mesocnt - Mesoscopic vdW potential for (carbon) nanotubes
mesocnt/viscous - Mesoscopic vdW potential for (carbon) nanotubes with friction
mgpt - Simplified model generalized pseudopotential theory (MGPT) potential
mie/cut - Mie potential
mliap - Multiple styles of machine-learning potential
mm3/switch3/coulgauss/long - Smoothed MM3 vdW potential with Gaussian electrostatics
momb - Many-Body Metal-Organic (MOMB) force field
morse - Morse potential
morse/smooth/linear - Linear smoothed Morse potential
morse/soft - Morse potential with a soft core
multi/lucy - DPD potential with density-dependent force
multi/lucy/rx - reactive DPD potential with density-dependent force
nb3b/harmonic - Non-bonded 3-body harmonic potential
nb3b/screened - Non-bonded 3-body screened harmonic potential
nm/cut - N-M potential
nm/cut/coul/cut - N-M potential with cutoff Coulomb
nm/cut/coul/long - N-M potential with long-range Coulomb
nm/cut/split - Split 12-6 Lennard-Jones and N-M potential
pace - Atomic Cluster Expansion (ACE) machine-learning potential
pace/extrapolation - Atomic Cluster Expansion (ACE) machine-learning potential with extrapolation grades
pedone - Pedone (PMMCS) potential (non-Coulomb part)
pod - Proper orthogonal decomposition (POD) machine-learning potential
peri/eps - Peridynamic EPS potential
peri/lps - Peridynamic LPS potential
peri/pmb - Peridynamic PMB potential
peri/ves - Peridynamic VES potential
polymorphic - Polymorphic 3-body potential
python -
quip -
rann -
reaxff - ReaxFF potential
rebo - Second generation REBO potential of Brenner
rebomos - REBOMoS potential for MoS2
rheo - fluid interactions in RHEO package
rheo/solid - solid interactions in RHEO package
resquared - Everaers RE-Squared ellipsoidal potential
saip/metal - Interlayer potential for hetero-junctions formed with hexagonal 2D materials and metal surfaces
sdpd/taitwater/isothermal - Smoothed dissipative particle dynamics for water at isothermal conditions
smatb - Second Moment Approximation to the Tight Binding
smatb/single - Second Moment Approximation to the Tight Binding for single-element systems
smtbq -
snap - SNAP machine-learning potential
soft - Soft (cosine) potential
sph/lj -
spin/dmi -
srp -
sw - Stillinger-Weber 3-body potential
sw/angle/table - Stillinger-Weber potential with tabulated angular term
sw/mod - modified Stillinger-Weber 3-body potential
table - tabulated pair potential
table/rx -
tdpd - tDPD particle interactions
tersoff - Tersoff 3-body potential
tersoff/mod - modified Tersoff 3-body potential
tersoff/zbl - Tersoff/ZBL 3-body potential
thole - Coulomb interactions with thole damping
threebody/table - generic tabulated three-body potential
tip4p/cut - Coulomb for TIP4P water w/out LJ
tip4p/long - long-range Coulomb for TIP4P water w/out LJ
tracker - monitor information about pairwise interactions
tri/lj - LJ potential between triangles
ufm -
uf3 - UF3 machine-learning potential
vashishta - Vashishta 2-body and 3-body potential
wf/cut - Wang-Frenkel Potential for short-ranged interactions
ylz - Yuan-Li-Zhang Potential for anisotropic interactions
yukawa - Yukawa potential
yukawa/colloid - screened Yukawa potential for finite-size particles
zbl - Ziegler-Biersack-Littmark potential
Restrictions
This command must be used before any coefficients are set by the pair_coeff, read_data, or read_restart commands.
Some pair styles are part of specific packages. They are only enabled if LAMMPS was built with that package. See the Build package page for more info. The doc pages for individual pair potentials tell if it is part of a package.
Default
pair_style none