forked from lijiext/lammps
143 lines
4.4 KiB
Plaintext
143 lines
4.4 KiB
Plaintext
.. index:: pair_style lj/smooth
|
|
|
|
pair_style lj/smooth command
|
|
============================
|
|
|
|
pair_style lj/smooth/cuda command
|
|
=================================
|
|
|
|
pair_style lj/smooth/omp command
|
|
================================
|
|
|
|
Syntax
|
|
""""""
|
|
|
|
.. parsed-literal::
|
|
|
|
pair_style lj/smooth Rin Rc
|
|
|
|
* Rin = inner cutoff beyond which force smoothing will be applied (distance units)
|
|
* Rc = outer cutoff for lj/smooth interactions (distance units)
|
|
|
|
Examples
|
|
""""""""
|
|
|
|
.. parsed-literal::
|
|
|
|
pair_style lj/smooth 8.0 10.0
|
|
pair_coeff * * 10.0 1.5
|
|
pair_coeff 1 1 20.0 1.3 7.0 9.0
|
|
|
|
Description
|
|
"""""""""""
|
|
|
|
Style *lj/smooth* computes a LJ interaction with a force smoothing
|
|
applied between the inner and outer cutoff.
|
|
|
|
.. image:: Eqs/pair_lj_smooth.jpg
|
|
:align: center
|
|
|
|
The polynomial coefficients C1, C2, C3, C4 are computed by LAMMPS to
|
|
cause the force to vary smoothly from the inner cutoff Rin to the
|
|
outer cutoff Rc.
|
|
|
|
At the inner cutoff the force and its 1st derivative
|
|
will match the unsmoothed LJ formula. At the outer cutoff the force
|
|
and its 1st derivative will be 0.0. The inner cutoff cannot be 0.0.
|
|
|
|
.. note::
|
|
|
|
this force smoothing causes the energy to be discontinuous both
|
|
in its values and 1st derivative. This can lead to poor energy
|
|
conservation and may require the use of a thermostat. Plot the energy
|
|
and force resulting from this formula via the
|
|
:doc:`pair_write <pair_write>` command to see the effect.
|
|
|
|
The following coefficients must be defined for each pair of atoms
|
|
types via the :doc:`pair_coeff <pair_coeff>` command as in the examples
|
|
above, or in the data file or restart files read by the
|
|
:doc:`read_data <read_data>` or :doc:`read_restart <read_restart>`
|
|
commands, or by mixing as described below:
|
|
|
|
* epsilon (energy units)
|
|
* sigma (distance units)
|
|
* innner (distance units)
|
|
* outer (distance units)
|
|
|
|
The last 2 coefficients are optional inner and outer cutoffs. If not
|
|
specified, the global values for Rin and Rc are used.
|
|
|
|
|
|
----------
|
|
|
|
|
|
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 :doc:`Section_accelerate <Section_accelerate>`
|
|
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 :ref:`Making LAMMPS <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 :ref:`-suffix command-line switch <start_7>` when you invoke LAMMPS, or you can
|
|
use the :doc:`suffix <suffix>` command in your input script.
|
|
|
|
See :doc:`Section_accelerate <Section_accelerate>` of the manual for
|
|
more instructions on how to use the accelerated styles effectively.
|
|
|
|
|
|
----------
|
|
|
|
|
|
**Mixing, shift, table, tail correction, restart, rRESPA info**:
|
|
|
|
For atom type pairs I,J and I != J, the epsilon, sigma, Rin
|
|
coefficients and the cutoff distance for this pair style can be mixed.
|
|
Rin is a cutoff value and is mixed like the cutoff. The other
|
|
coefficients are mixed according to the pair_modify mix option. The
|
|
default mix value is *geometric*. See the "pair_modify" command for
|
|
details.
|
|
|
|
This pair style supports the :doc:`pair_modify <pair_modify>` shift
|
|
option for the energy of the pair interaction.
|
|
|
|
The :doc:`pair_modify <pair_modify>` table option is not relevant
|
|
for this pair style.
|
|
|
|
This pair style does not support the :doc:`pair_modify <pair_modify>`
|
|
tail option for adding long-range tail corrections to energy and
|
|
pressure, since the energy of the pair interaction is smoothed to 0.0
|
|
at the cutoff.
|
|
|
|
This pair style writes its information to :doc:`binary restart files <restart>`, so pair_style and pair_coeff commands do not need
|
|
to be specified in an input script that reads a restart file.
|
|
|
|
This pair style can only be used via the *pair* keyword of the
|
|
:doc:`run_style respa <run_style>` command. It does not support the
|
|
*inner*, *middle*, *outer* keywords.
|
|
|
|
|
|
----------
|
|
|
|
|
|
Restrictions
|
|
""""""""""""
|
|
none
|
|
|
|
Related commands
|
|
""""""""""""""""
|
|
|
|
:doc:`pair_coeff <pair_coeff>`, :doc:`pair lj/smooth/linear <pair_lj_smooth_linear>`
|
|
|
|
**Default:** none
|
|
|
|
|
|
.. _lws: http://lammps.sandia.gov
|
|
.. _ld: Manual.html
|
|
.. _lc: Section_commands.html#comm
|