"LAMMPS WWW Site"_lws - "LAMMPS Documentation"_ld - "LAMMPS Commands"_lc :c

:link(lws,http://lammps.sandia.gov)
:link(ld,Manual.html)
:link(lc,Section_commands.html#comm)

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bond_style fene/expand command :h3
bond_style fene/expand/omp command :h3

[Syntax:]

bond_style fene/expand :pre

[Examples:]

bond_style fene/expand
bond_coeff 1 30.0 1.5 1.0 1.0 0.5 :pre

[Description:]

The {fene/expand} bond style uses the potential

:c,image(Eqs/bond_fene_expand.jpg)

to define a finite extensible nonlinear elastic (FENE) potential
"(Kremer)"_#Kremer, used for bead-spring polymer models.  The first
term is attractive, the 2nd Lennard-Jones term is repulsive.

The {fene/expand} bond style is similar to {fene} except that an extra
shift factor of delta (positive or negative) is added to {r} to
effectively change the bead size of the bonded atoms.  The first term
now extends to R0 + delta and the 2nd term is cutoff at 2^(1/6) sigma
+ delta.

The following coefficients must be defined for each bond type via the
"bond_coeff"_bond_coeff.html command as in the example above, or in
the data file or restart files read by the "read_data"_read_data.html
or "read_restart"_read_restart.html commands:

K (energy/distance^2)
R0 (distance)
epsilon (energy)
sigma (distance)
delta (distance) :ul

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Styles with a {cuda}, {gpu}, {intel}, {kk}, {omp}, or {opt} suffix are
functionally the same as the corresponding style without the suffix.
They have been optimized to run faster, depending on your available
hardware, as discussed in "Section_accelerate"_Section_accelerate.html
of the manual.  The accelerated styles take the same arguments and
should produce the same results, except for round-off and precision
issues.

These accelerated styles are part of the USER-CUDA, GPU, USER-INTEL,
KOKKOS, USER-OMP and OPT packages, respectively.  They are only
enabled if LAMMPS was built with those packages.  See the "Making
LAMMPS"_Section_start.html#start_3 section for more info.

You can specify the accelerated styles explicitly in your input script
by including their suffix, or you can use the "-suffix command-line
switch"_Section_start.html#start_7 when you invoke LAMMPS, or you can
use the "suffix"_suffix.html command in your input script.

See "Section_accelerate"_Section_accelerate.html of the manual for
more instructions on how to use the accelerated styles effectively.

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[Restrictions:]

This bond style can only be used if LAMMPS was built with the
MOLECULE package (which it is by default).  See the "Making
LAMMPS"_Section_start.html#start_3 section for more info on packages.

You typically should specify "special_bonds fene"_special_bonds.html"
or "special_bonds lj/coul 0 1 1"_special_bonds.html to use this bond
style.  LAMMPS will issue a warning it that's not the case.

[Related commands:]

"bond_coeff"_bond_coeff.html, "delete_bonds"_delete_bonds.html

[Default:] none

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:link(Kremer)
[(Kremer)] Kremer, Grest, J Chem Phys, 92, 5057 (1990).
