forked from lijiext/lammps
92 lines
2.9 KiB
Plaintext
92 lines
2.9 KiB
Plaintext
"LAMMPS WWW Site"_lws - "LAMMPS Documentation"_ld - "LAMMPS Commands"_lc :c
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:link(lws,http://lammps.sandia.gov)
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:link(ld,Manual.html)
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:link(lc,Section_commands.html#comm)
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:line
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bond_style fene/expand command :h3
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bond_style fene/expand/omp command :h3
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[Syntax:]
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bond_style fene/expand :pre
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[Examples:]
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bond_style fene/expand
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bond_coeff 1 30.0 1.5 1.0 1.0 0.5 :pre
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[Description:]
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The {fene/expand} bond style uses the potential
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:c,image(Eqs/bond_fene_expand.jpg)
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to define a finite extensible nonlinear elastic (FENE) potential
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"(Kremer)"_#Kremer, used for bead-spring polymer models. The first
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term is attractive, the 2nd Lennard-Jones term is repulsive.
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The {fene/expand} bond style is similar to {fene} except that an extra
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shift factor of delta (positive or negative) is added to {r} to
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effectively change the bead size of the bonded atoms. The first term
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now extends to R0 + delta and the 2nd term is cutoff at 2^(1/6) sigma
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+ delta.
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The following coefficients must be defined for each bond type via the
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"bond_coeff"_bond_coeff.html command as in the example above, or in
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the data file or restart files read by the "read_data"_read_data.html
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or "read_restart"_read_restart.html commands:
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K (energy/distance^2)
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R0 (distance)
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epsilon (energy)
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sigma (distance)
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delta (distance) :ul
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:line
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Styles with a {cuda}, {gpu}, {omp}, or {opt} suffix are functionally
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the same as the corresponding style without the suffix. They have
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been optimized to run faster, depending on your available hardware, as
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discussed in "Section_accelerate"_Section_accelerate.html of the
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manual. The accelerated styles take the same arguments and should
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produce the same results, except for round-off and precision issues.
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These accelerated styles are part of the USER-CUDA, GPU, USER-OMP and OPT
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packages, respectively. They are only enabled if LAMMPS was built with
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those packages. See the "Making LAMMPS"_Section_start.html#start_3
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section for more info.
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You can specify the accelerated styles explicitly in your input script
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by including their suffix, or you can use the "-suffix command-line
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switch"_Section_start.html#start_7 when you invoke LAMMPS, or you can
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use the "suffix"_suffix.html command in your input script.
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See "Section_accelerate"_Section_accelerate.html of the manual for
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more instructions on how to use the accelerated styles effectively.
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:line
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[Restrictions:]
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This bond style can only be used if LAMMPS was built with the
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MOLECULAR package (which it is by default). See the "Making
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LAMMPS"_Section_start.html#start_3 section for more info on packages.
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You typically should specify "special_bonds fene"_special_bonds.html"
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or "special_bonds lj/coul 0 1 1"_special_bonds.html to use this bond
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style. LAMMPS will issue a warning it that's not the case.
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[Related commands:]
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"bond_coeff"_bond_coeff.html, "delete_bonds"_delete_bonds.html
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[Default:] none
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:line
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:link(Kremer)
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[(Kremer)] Kremer, Grest, J Chem Phys, 92, 5057 (1990).
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