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.. index:: pair_style zbl
pair_style zbl command
======================
pair_style zbl/gpu command
==========================
pair_style zbl/omp command
==========================
Syntax
""""""
.. parsed-literal::
pair_style zbl inner outer
* inner = distance where switching function begins
* outer = global cutoff for ZBL interaction
Examples
""""""""
.. parsed-literal::
pair_style zbl 3.0 4.0
pair_coeff * * 73.0 73.0
pair_coeff 1 1 14.0 14.0
Description
"""""""""""
Style *zbl* computes the Ziegler-Biersack-Littmark (ZBL) screened nuclear
repulsion for describing high-energy collisions between atoms.
:ref:`(Ziegler) <Ziegler>`. It includes an additional switching function
that ramps the energy, force, and curvature smoothly to zero
between an inner and outer cutoff. The potential
energy due to a pair of atoms at a distance r_ij is given by:
.. image:: Eqs/pair_zbl.jpg
:align: center
where e is the electron charge, epsilon_0 is the electrical
permittivity of vacuum, and Z_i and Z_j are the nuclear charges of the
two atoms. The switching function S(r) is identical to that used by
:doc:`pair_style lj/gromacs <pair_gromacs>`. Here, the inner and outer
cutoff are the same for all pairs of atom types.
The following coefficients must be defined for each pair of atom types
via the :doc:`pair_coeff <pair_coeff>` command as in the examples above,
or in the LAMMPS data file.
* Z_i (atomic number for first atom type, e.g. 13.0 for aluminum)
* Z_j (ditto for second atom type)
The values of Z_i and Z_j are normally equal to the atomic
numbers of the two atom types. Thus, the user may optionally
specify only the coefficients for each I==I pair, and rely
on the obvious mixing rule for cross interactions (see below).
Note that when I==I it is required that Z_i == Z_j. When used
with :doc:`hybrid/overlay <pair_hybrid>` and pairs are assigned
to more than one sub-style, the mixing rule is not used and
each pair of types interacting with the ZBL sub-style must
be included in a pair_coeff command.
.. note::
The numerical values of the exponential decay constants in the
screening function depend on the unit of distance. In the above
equation they are given for units of angstroms. LAMMPS will
automatically convert these values to the distance unit of the
specified LAMMPS :doc:`units <units>` setting. The values of Z should
always be given as multiples of a proton's charge, e.g. 29.0 for
copper.
----------
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 Z_i and Z_j coefficients
can be mixed by taking Z_i and Z_j from the values specified for
I == I and J == J cases. When used
with :doc:`hybrid/overlay <pair_hybrid>` and pairs are assigned
to more than one sub-style, the mixing rule is not used and
each pair of types interacting with the ZBL sub-style
must be included in a pair_coeff command.
The :doc:`pair_modify <pair_modify>` mix option has no effect on
the mixing behavior
The ZBL pair style does not support the :doc:`pair_modify <pair_modify>`
shift option, since the ZBL interaction is already smoothed to 0.0 at
the cutoff.
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 there are no corrections for a potential that goes to
0.0 at the cutoff.
This pair style does not write information to :doc:`binary restart files <restart>`, so pair_style and pair_coeff commands must 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>`
**Default:** none
----------
.. _Ziegler:
**(Ziegler)** J.F. Ziegler, J. P. Biersack and U. Littmark, "The
Stopping and Range of Ions in Matter," Volume 1, Pergamon, 1985.
.. _lws: http://lammps.sandia.gov
.. _ld: Manual.html
.. _lc: Section_commands.html#comm
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