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pair_style meam/spline
======================
pair_style meam/spline/omp
==========================
Syntax
""""""
.. parsed-literal::
pair_style meam/spline
Examples
""""""""
.. parsed-literal::
pair_style meam/spline
pair_coeff * * Ti.meam.spline Ti
pair_coeff * * Ti.meam.spline Ti Ti Ti
Description
"""""""""""
The *meam/spline* style computes pairwise interactions for metals
using a variant of modified embedded-atom method (MEAM) potentials
:ref:`(Lenosky) <Lenosky>`. The total energy E is given by
.. image:: Eqs/pair_meam_spline.jpg
:align: center
where rho_i is the density at atom I, theta_jik is the angle between
atoms J, I, and K centered on atom I. The five functions Phi, U, rho,
f, and g are represented by cubic splines.
The cutoffs and the coefficients for these spline functions are listed
in a parameter file which is specified by the
:doc:`pair_coeff <pair_coeff>` command. Parameter files for different
elements are included in the "potentials" directory of the LAMMPS
distribution and have a ".meam.spline" file suffix. All of these
files are parameterized in terms of LAMMPS :doc:`metal units <units>`.
Note that unlike for other potentials, cutoffs for spline-based MEAM
potentials are not set in the pair_style or pair_coeff command; they
are specified in the potential files themselves.
Unlike the EAM pair style, which retrieves the atomic mass from the
potential file, the spline-based MEAM potentials do not include mass
information; thus you need to use the :doc:`mass <mass>` command to
specify it.
Only a single pair_coeff command is used with the *meam/spline* style
which specifies a potential file with parameters for all needed
elements. These are mapped to LAMMPS atom types by specifying N
additional arguments after the filename in the pair_coeff command,
where N is the number of LAMMPS atom types:
* filename
* N element names = mapping of spline-based MEAM elements to atom types
See the :doc:`pair_coeff <pair_coeff>` doc page for alternate ways
to specify the path for the potential file.
As an example, imagine the Ti.meam.spline file has values for Ti. If
your LAMMPS simulation has 3 atoms types and they are all to be
treated with this potentials, you would use the following pair_coeff
command:
.. parsed-literal::
pair_coeff * * Ti.meam.spline Ti Ti Ti
The 1st 2 arguments must be * * so as to span all LAMMPS atom types.
The three Ti arguments map LAMMPS atom types 1,2,3 to the Ti element
in the potential file. If a mapping value is specified as NULL, the
mapping is not performed. This can be used when a *meam/spline*
potential is used as part of the *hybrid* pair style. The NULL values
are placeholders for atom types that will be used with other
potentials.
.. note::
The *meam/spline* style currently supports only single-element
MEAM potentials. It may be extended for alloy systems in the future.
----------
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**:
The current version of this pair style does not support multiple
element types or mixing. It has been designed for pure elements only.
This pair style does not support the :doc:`pair_modify <pair_modify>`
shift, table, and tail options.
The *meam/spline* pair style does not write its information to :doc:`binary restart files <restart>`, since it is stored in an external
potential parameter file. Thus, you need to re-specify the pair_style
and pair_coeff commands in an input script that reads a restart file.
The *meam/spline* pair style can only be used via the *pair* keyword of the
:doc:`run_style respa <run_style>` command. They do not support the
*inner*, *middle*, *outer* keywords.
----------
Restrictions
""""""""""""
This pair style requires the :doc:`newton <newton>` setting to be "on"
for pair interactions.
This pair style is only enabled if LAMMPS was built with the USER-MISC
package. See the :ref:`Making LAMMPS <start_3>` section
for more info.
Related commands
""""""""""""""""
:doc:`pair_coeff <pair_coeff>`, :doc:`pair_style meam <pair_meam>`
**Default:** none
----------
.. _Lenosky:
**(Lenosky)** Lenosky, Sadigh, Alonso, Bulatov, de la Rubia, Kim, Voter,
Kress, Modelling Simulation Materials Science Enginerring, 8, 825
(2000).
.. _lws: http://lammps.sandia.gov
.. _ld: Manual.html
.. _lc: Section_commands.html#comm
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