lammps/doc/pair_hybrid.txt

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pair_style hybrid command :h3

[Syntax:]

pair_style hybrid style1 style2 ... :pre

style1,style2 = list of one or more pair styles :ul

[Examples:]

pair_style hybrid lj/charmm/coul/long 10.0 eam
pair_coeff 1*2 1*2 eam niu3
pair_coeff 3 3 lj/cut/coul/cut 1.0 1.0
pair_coeff 1*2 3 lj/cut 0.5 1.2 :pre

[Description:]

The {hybrid} style enables the use of multiple pair styles in one
simulation.  A pair style can be assigned to each pair of atom types
via the "pair_coeff"_pair_coeff.html command.

For example, a metal on a LJ surface could be computed where the metal
atoms interact with each other via a {eam} potential, the surface
atoms interact with each other via a {lj/cut} potential, and the
metal/surface interaction is also via a {lj/cut} potential.

All pair styles that will be used must be listed in the pair_style
hybrid command (in any order).  The name of each sub-style is followed
by its arguments, as illustrated in the example above.

In the pair_coeff command, the first coefficient sets the pair style
and the remaining coefficients are those appropriate to that style.
For example, consider a simulation with 3 atom types: types 1 and 2
are Ni atoms, type 3 are LJ atoms with charges.  The following
commands would set up a hybrid simulation:

pair_style hybrid eam/alloy lj/cut/coul/cut 10.0 lj/cut 8.0
pair_coeff * * eam/alloy nialhjea 1 1 0
pair_coeff 3 3 lj/cut/coul/cut 1.0 1.0
pair_coeff 1*2 3 lj/cut 0.8 1.1 :pre

If the pair_coeff command for a sub-style requires the use of * * as
atom type arguments (e.g. the {eam/alloy} example above), then it will
also include trailing arguments which map atom types to elements in
the potential.  These mapping arguments should be specified as 0 if
the sub-style is not being applied to certain atom types.

Note that you may also need to use an "atom_style"_atom_style.html
hybrid command in your input script, if atoms in the simulation will
have attributes from several atom styles, due to using multiple pair
potentials.

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[Mixing, shift, table, tail correction, per-atom energy/stress, and
restart info]:

Any pair potential settings made via the
"pair_modify"_pair_modify.html command are passed along to all
sub-styles of the hybrid potential.

For atom type pairs I,J and I != J, if the sub-style assigned to I,I
and J,J is the same, and if the sub-style allows for mixing, then the
coefficients for I,J can be mixed.  The default mix value is
{geometric}.  See the "pair_modify" command for details.  See the
See the doc page for the sub-style to see if allows for mixing.

The hybrid pair style supports the "pair_modify"_pair_modify.html
shift, table, and tail options for an I,J pair interaction, if the
associated sub-style supports it.

The hybrid pair style can calculate per-atom energy and stress, as
used by the "compute epair/atom"_compute_epair_atom.html, "compute
stress/atom"_compute_stress_atom.html, and "dump custom"_dump.html
commands, if all its sub-styles can perform per-atom calculations.

For the hybrid pair style, the list of sub-styles and their respective
settings are written to "binary restart files"_restart.html, so a
pair_style command does not need to specified in an input script that
reads a restart file.  However, the coefficient information is not
stored in the restart file.  Thus, pair_coeff commands do need to be
specified in the restart input script.

[Restrictions:]

A pair style of {none} can be specified as an argument to pair_style
hybrid and the corresponding pair_coeff commands, if you desire to
turn off pairwise interactions between certain pairs of atom types.

When using a long-range Coulomic solver (via the
"kspace_style"_kspace_style command) with pair_style hybrid, one or
more sub-styles will be of the "long" variety.
E.g. {lj/cut/coul/long} or {buck/coul/long}.  It is OK to have more
than one sub-style with a "long" component, but you must insure that
the short-range Coulombic cutoff used by each of these pair styles is
consistent.  Else the long-range Coulombic solve will be inconsistent.

[Related commands:]

"pair_coeff"_pair_coeff.html

[Default:] none