forked from lijiext/lammps
113 lines
2.9 KiB
Plaintext
113 lines
2.9 KiB
Plaintext
.. index:: bond_style fene
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bond_style fene command
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=======================
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bond_style fene/intel command
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=============================
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bond_style fene/kk command
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==========================
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bond_style fene/omp command
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===========================
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Syntax
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""""""
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.. parsed-literal::
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bond_style fene
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Examples
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""""""""
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.. parsed-literal::
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bond_style fene
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bond_coeff 1 30.0 1.5 1.0 1.0
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Description
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"""""""""""
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The *fene* bond style uses the potential
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.. image:: Eqs/bond_fene.jpg
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:align: center
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to define a finite extensible nonlinear elastic (FENE) potential
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:ref:`(Kremer) <fene-Kremer>`, used for bead-spring polymer models. The first
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term is attractive, the 2nd Lennard-Jones term is repulsive. The
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first term extends to R0, the maximum extent of the bond. The 2nd
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term is cutoff at 2^(1/6) sigma, the minimum of the LJ potential.
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The following coefficients must be defined for each bond type via the
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:doc:`bond_coeff <bond_coeff>` command as in the example above, or in
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the data file or restart files read by the :doc:`read_data <read_data>`
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or :doc:`read_restart <read_restart>` 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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----------
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Styles with a *gpu*\ , *intel*\ , *kk*\ , *omp*\ , or *opt* suffix are
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functionally the same as the corresponding style without the suffix.
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They have been optimized to run faster, depending on your available
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hardware, as discussed in :doc:`Section_accelerate <Section_accelerate>`
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of the manual. The accelerated styles take the same arguments and
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should produce the same results, except for round-off and precision
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issues.
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These accelerated styles are part of the GPU, USER-INTEL, KOKKOS,
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USER-OMP and OPT packages, respectively. They are only enabled if
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LAMMPS was built with those packages. See the :ref:`Making LAMMPS <start_3>` 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 :ref:`-suffix command-line switch <start_7>` when you invoke LAMMPS, or you can
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use the :doc:`suffix <suffix>` command in your input script.
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See :doc:`Section_accelerate <Section_accelerate>` of the manual for
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more instructions on how to use the accelerated styles effectively.
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----------
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Restrictions
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""""""""""""
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This bond style can only be used if LAMMPS was built with the
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MOLECULE package (which it is by default). See the :ref:`Making LAMMPS <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 :doc:`special_bonds lj/coul 0 1 1 <special_bonds>` 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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""""""""""""""""
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:doc:`bond_coeff <bond_coeff>`, :doc:`delete_bonds <delete_bonds>`
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**Default:** none
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----------
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.. _fene-Kremer:
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**(Kremer)** Kremer, Grest, J Chem Phys, 92, 5057 (1990).
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.. _lws: http://lammps.sandia.gov
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.. _ld: Manual.html
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.. _lc: Section_commands.html#comm
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