1 "LAMMPS WWW Site"_lws - "LAMMPS Documentation"_ld - "LAMMPS Commands"_lc :c
3 :link(lws,http://lammps.sandia.gov)
5 :link(lc,Section_commands.html#comm)
9 pair_style lj/cut command :h3
10 pair_style lj/cut/gpu command :h3
11 pair_style lj/cut/intel command :h3
12 pair_style lj/cut/kk command :h3
13 pair_style lj/cut/opt command :h3
14 pair_style lj/cut/omp command :h3
15 pair_style lj/cut/coul/cut command :h3
16 pair_style lj/cut/coul/cut/gpu command :h3
17 pair_style lj/cut/coul/cut/omp command :h3
18 pair_style lj/cut/coul/debye command :h3
19 pair_style lj/cut/coul/debye/gpu command :h3
20 pair_style lj/cut/coul/debye/kk command :h3
21 pair_style lj/cut/coul/debye/omp command :h3
22 pair_style lj/cut/coul/dsf command :h3
23 pair_style lj/cut/coul/dsf/gpu command :h3
24 pair_style lj/cut/coul/dsf/kk command :h3
25 pair_style lj/cut/coul/dsf/omp command :h3
26 pair_style lj/cut/coul/long command :h3
27 pair_style lj/cut/coul/long/cs command :h3
28 pair_style lj/cut/coul/long/gpu command :h3
29 pair_style lj/cut/coul/long/intel command :h3
30 pair_style lj/cut/coul/long/opt command :h3
31 pair_style lj/cut/coul/long/omp command :h3
32 pair_style lj/cut/coul/msm command :h3
33 pair_style lj/cut/coul/msm/gpu command :h3
34 pair_style lj/cut/coul/msm/omp command :h3
35 pair_style lj/cut/tip4p/cut command :h3
36 pair_style lj/cut/tip4p/cut/omp command :h3
37 pair_style lj/cut/tip4p/long command :h3
38 pair_style lj/cut/tip4p/long/omp command :h3
39 pair_style lj/cut/tip4p/long/opt command :h3
43 pair_style style args :pre
45 style = {lj/cut} or {lj/cut/coul/cut} or {lj/cut/coul/debye} or {lj/cut/coul/dsf} or {lj/cut/coul/long} or {lj/cut/coul/long/cs} or {lj/cut/coul/msm} or {lj/cut/tip4p/long}
46 args = list of arguments for a particular style :ul
47 {lj/cut} args = cutoff
48 cutoff = global cutoff for Lennard Jones interactions (distance units)
49 {lj/cut/coul/cut} args = cutoff (cutoff2)
50 cutoff = global cutoff for LJ (and Coulombic if only 1 arg) (distance units)
51 cutoff2 = global cutoff for Coulombic (optional) (distance units)
52 {lj/cut/coul/debye} args = kappa cutoff (cutoff2)
53 kappa = inverse of the Debye length (inverse distance units)
54 cutoff = global cutoff for LJ (and Coulombic if only 1 arg) (distance units)
55 cutoff2 = global cutoff for Coulombic (optional) (distance units)
56 {lj/cut/coul/dsf} args = alpha cutoff (cutoff2)
57 alpha = damping parameter (inverse distance units)
58 cutoff = global cutoff for LJ (and Coulombic if only 1 arg) (distance units)
59 cutoff2 = global cutoff for Coulombic (distance units)
60 {lj/cut/coul/long} args = cutoff (cutoff2)
61 cutoff = global cutoff for LJ (and Coulombic if only 1 arg) (distance units)
62 cutoff2 = global cutoff for Coulombic (optional) (distance units)
63 {lj/cut/coul/msm} args = cutoff (cutoff2)
64 cutoff = global cutoff for LJ (and Coulombic if only 1 arg) (distance units)
65 cutoff2 = global cutoff for Coulombic (optional) (distance units)
66 {lj/cut/tip4p/cut} args = otype htype btype atype qdist cutoff (cutoff2)
67 otype,htype = atom types for TIP4P O and H
68 btype,atype = bond and angle types for TIP4P waters
69 qdist = distance from O atom to massless charge (distance units)
70 cutoff = global cutoff for LJ (and Coulombic if only 1 arg) (distance units)
71 cutoff2 = global cutoff for Coulombic (optional) (distance units)
72 {lj/cut/tip4p/long} args = otype htype btype atype qdist cutoff (cutoff2)
73 otype,htype = atom types for TIP4P O and H
74 btype,atype = bond and angle types for TIP4P waters
75 qdist = distance from O atom to massless charge (distance units)
76 cutoff = global cutoff for LJ (and Coulombic if only 1 arg) (distance units)
77 cutoff2 = global cutoff for Coulombic (optional) (distance units) :pre
83 pair_coeff 1 1 1 1.1 2.8 :pre
85 pair_style lj/cut/coul/cut 10.0
86 pair_style lj/cut/coul/cut 10.0 8.0
87 pair_coeff * * 100.0 3.0
88 pair_coeff 1 1 100.0 3.5 9.0
89 pair_coeff 1 1 100.0 3.5 9.0 9.0 :pre
91 pair_style lj/cut/coul/debye 1.5 3.0
92 pair_style lj/cut/coul/debye 1.5 2.5 5.0
93 pair_coeff * * 1.0 1.0
94 pair_coeff 1 1 1.0 1.5 2.5
95 pair_coeff 1 1 1.0 1.5 2.5 5.0 :pre
97 pair_style lj/cut/coul/dsf 0.05 2.5 10.0
98 pair_coeff * * 1.0 1.0
99 pair_coeff 1 1 1.0 1.0 2.5 :pre
101 pair_style lj/cut/coul/long 10.0
102 pair_style lj/cut/coul/long/cs 10.0
103 pair_style lj/cut/coul/long 10.0 8.0
104 pair_style lj/cut/coul/long/cs 10.0 8.0
105 pair_coeff * * 100.0 3.0
106 pair_coeff 1 1 100.0 3.5 9.0 :pre
108 pair_style lj/cut/coul/msm 10.0
109 pair_style lj/cut/coul/msm 10.0 8.0
110 pair_coeff * * 100.0 3.0
111 pair_coeff 1 1 100.0 3.5 9.0 :pre
113 pair_style lj/cut/tip4p/cut 1 2 7 8 0.15 12.0
114 pair_style lj/cut/tip4p/cut 1 2 7 8 0.15 12.0 10.0
115 pair_coeff * * 100.0 3.0
116 pair_coeff 1 1 100.0 3.5 9.0 :pre
118 pair_style lj/cut/tip4p/long 1 2 7 8 0.15 12.0
119 pair_style lj/cut/tip4p/long 1 2 7 8 0.15 12.0 10.0
120 pair_coeff * * 100.0 3.0
121 pair_coeff 1 1 100.0 3.5 9.0 :pre
125 The {lj/cut} styles compute the standard 12/6 Lennard-Jones potential,
128 :c,image(Eqs/pair_lj.jpg)
132 Style {lj/cut/coul/cut} adds a Coulombic pairwise interaction given by
134 :c,image(Eqs/pair_coulomb.jpg)
136 where C is an energy-conversion constant, Qi and Qj are the charges on
137 the 2 atoms, and epsilon is the dielectric constant which can be set
138 by the "dielectric"_dielectric.html command. If one cutoff is
139 specified in the pair_style command, it is used for both the LJ and
140 Coulombic terms. If two cutoffs are specified, they are used as
141 cutoffs for the LJ and Coulombic terms respectively.
143 Style {lj/cut/coul/debye} adds an additional exp() damping factor
144 to the Coulombic term, given by
146 :c,image(Eqs/pair_debye.jpg)
148 where kappa is the inverse of the Debye length. This potential is
149 another way to mimic the screening effect of a polar solvent.
151 Style {lj/cut/coul/dsf} computes the Coulombic term via the damped
152 shifted force model described in "Fennell"_#Fennell, given by:
154 :c,image(Eqs/pair_coul_dsf.jpg)
156 where {alpha} is the damping parameter and erfc() is the complementary
157 error-function. This potential is essentially a short-range,
158 spherically-truncated, charge-neutralized, shifted, pairwise {1/r}
159 summation. The potential is based on Wolf summation, proposed as an
160 alternative to Ewald summation for condensed phase systems where
161 charge screening causes electrostatic interactions to become
162 effectively short-ranged. In order for the electrostatic sum to be
163 absolutely convergent, charge neutralization within the cutoff radius
164 is enforced by shifting the potential through placement of image
165 charges on the cutoff sphere. Convergence can often be improved by
166 setting {alpha} to a small non-zero value.
168 Styles {lj/cut/coul/long} and {lj/cut/coul/msm} compute the same
169 Coulombic interactions as style {lj/cut/coul/cut} except that an
170 additional damping factor is applied to the Coulombic term so it can
171 be used in conjunction with the "kspace_style"_kspace_style.html
172 command and its {ewald} or {pppm} option. The Coulombic cutoff
173 specified for this style means that pairwise interactions within this
174 distance are computed directly; interactions outside that distance are
175 computed in reciprocal space.
177 Style {lj/cut/coul/long/cs} is identical to {lj/cut/coul/long} except
178 that a term is added for the "core/shell
179 model"_Section_howto.html#howto_25 to allow charges on core and shell
180 particles to be separated by r = 0.0.
182 Styles {lj/cut/tip4p/cut} and {lj/cut/tip4p/long} implement the TIP4P
183 water model of "(Jorgensen)"_#Jorgensen, which introduces a massless
184 site located a short distance away from the oxygen atom along the
185 bisector of the HOH angle. The atomic types of the oxygen and
186 hydrogen atoms, the bond and angle types for OH and HOH interactions,
187 and the distance to the massless charge site are specified as
188 pair_style arguments. Style {lj/cut/tip4p/cut} uses a cutoff for
189 Coulomb interactions; style {lj/cut/tip4p/long} is for use with a
190 long-range Coulombic solver (Ewald or PPPM).
192 NOTE: For each TIP4P water molecule in your system, the atom IDs for
193 the O and 2 H atoms must be consecutive, with the O atom first. This
194 is to enable LAMMPS to "find" the 2 H atoms associated with each O
195 atom. For example, if the atom ID of an O atom in a TIP4P water
196 molecule is 500, then its 2 H atoms must have IDs 501 and 502.
198 See the "howto section"_Section_howto.html#howto_8 for more
199 information on how to use the TIP4P pair styles and lists of
200 parameters to set. Note that the neighobr list cutoff for Coulomb
201 interactions is effectively extended by a distance 2*qdist when using
202 the TIP4P pair style, to account for the offset distance of the
203 fictitious charges on O atoms in water molecules. Thus it is
204 typically best in an efficiency sense to use a LJ cutoff >= Coulomb
205 cutoff + 2*qdist, to shrink the size of the neighbor list. This leads
206 to slightly larger cost for the long-range calculation, so you can
207 test the trade-off for your model.
209 For all of the {lj/cut} pair styles, the following coefficients must
210 be defined for each pair of atoms types via the
211 "pair_coeff"_pair_coeff.html command as in the examples above, or in
212 the data file or restart files read by the "read_data"_read_data.html
213 or "read_restart"_read_restart.html commands, or by mixing as
216 epsilon (energy units)
217 sigma (distance units)
218 cutoff1 (distance units)
219 cutoff2 (distance units) :ul
221 Note that sigma is defined in the LJ formula as the zero-crossing
222 distance for the potential, not as the energy minimum at 2^(1/6)
225 The latter 2 coefficients are optional. If not specified, the global
226 LJ and Coulombic cutoffs specified in the pair_style command are used.
227 If only one cutoff is specified, it is used as the cutoff for both LJ
228 and Coulombic interactions for this type pair. If both coefficients
229 are specified, they are used as the LJ and Coulombic cutoffs for this
230 type pair. You cannot specify 2 cutoffs for style {lj/cut}, since it
231 has no Coulombic terms.
233 For {lj/cut/coul/long} and {lj/cut/coul/msm} and {lj/cut/tip4p/cut}
234 and {lj/cut/tip4p/long} only the LJ cutoff can be specified since a
235 Coulombic cutoff cannot be specified for an individual I,J type pair.
236 All type pairs use the same global Coulombic cutoff specified in the
241 Styles with a {gpu}, {intel}, {kk}, {omp}, or {opt} suffix are
242 functionally the same as the corresponding style without the suffix.
243 They have been optimized to run faster, depending on your available
244 hardware, as discussed in "Section 5"_Section_accelerate.html
245 of the manual. The accelerated styles take the same arguments and
246 should produce the same results, except for round-off and precision
249 These accelerated styles are part of the GPU, USER-INTEL, KOKKOS,
250 USER-OMP and OPT packages, respectively. They are only enabled if
251 LAMMPS was built with those packages. See the "Making
252 LAMMPS"_Section_start.html#start_3 section for more info.
254 You can specify the accelerated styles explicitly in your input script
255 by including their suffix, or you can use the "-suffix command-line
256 switch"_Section_start.html#start_7 when you invoke LAMMPS, or you can
257 use the "suffix"_suffix.html command in your input script.
259 See "Section 5"_Section_accelerate.html of the manual for
260 more instructions on how to use the accelerated styles effectively.
264 [Mixing, shift, table, tail correction, restart, rRESPA info]:
266 For atom type pairs I,J and I != J, the epsilon and sigma coefficients
267 and cutoff distance for all of the lj/cut pair styles can be mixed.
268 The default mix value is {geometric}. See the "pair_modify" command
271 All of the {lj/cut} pair styles support the
272 "pair_modify"_pair_modify.html shift option for the energy of the
273 Lennard-Jones portion of the pair interaction.
275 The {lj/cut/coul/long} and {lj/cut/tip4p/long} pair styles support the
276 "pair_modify"_pair_modify.html table option since they can tabulate
277 the short-range portion of the long-range Coulombic interaction.
279 All of the {lj/cut} pair styles support the
280 "pair_modify"_pair_modify.html tail option for adding a long-range
281 tail correction to the energy and pressure for the Lennard-Jones
282 portion of the pair interaction.
284 All of the {lj/cut} pair styles write their information to "binary
285 restart files"_restart.html, so pair_style and pair_coeff commands do
286 not need to be specified in an input script that reads a restart file.
288 The {lj/cut} and {lj/cut/coul/long} pair styles support the use of the
289 {inner}, {middle}, and {outer} keywords of the "run_style
290 respa"_run_style.html command, meaning the pairwise forces can be
291 partitioned by distance at different levels of the rRESPA hierarchy.
292 The other styles only support the {pair} keyword of run_style respa.
293 See the "run_style"_run_style.html command for details.
299 The {lj/cut/coul/long} and {lj/cut/tip4p/long} styles are part of the
300 KSPACE package. The {lj/cut/tip4p/cut} style is part of the MOLECULE
301 package. These styles are only enabled if LAMMPS was built with those
302 packages. See the "Making LAMMPS"_Section_start.html#start_3 section
303 for more info. Note that the KSPACE and MOLECULE packages are
304 installed by default.
308 "pair_coeff"_pair_coeff.html
315 [(Jorgensen)] Jorgensen, Chandrasekhar, Madura, Impey, Klein, J Chem
316 Phys, 79, 926 (1983).
319 [(Fennell)] C. J. Fennell, J. D. Gezelter, J Chem Phys, 124,