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update pair meam/spline docs to reflect limitations of the implementation

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this closes #2500
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Axel Kohlmeyer
2020-12-01 19:06:54 -05:00
parent 63d8182ff3
commit 71827f0099
1 changed files with 15 additions and 14 deletions
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29
doc/src/pair_meam_spline.rst
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@ -20,7 +20,7 @@ Examples
pair_style meam/spline
pair_coeff * * Ti.meam.spline Ti
pair_coeff * * Ti.meam.spline Ti Ti Ti
pair_coeff * * Ti.meam.spline Ti O
Description
"""""""""""
@ -84,23 +84,22 @@ where N is the number of LAMMPS 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 (old style). 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:
As an example, imagine the Ti.meam.spline file has values for Ti (old style).
In that case your LAMMPS simulation may only have one atom type which has
to be mapped to the Ti element as follows:
.. code-block:: LAMMPS
pair_coeff * * Ti.meam.spline Ti Ti Ti
pair_coeff * * Ti.meam.spline Ti
The first 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. The old-style potential maps any non-NULL species named
on the command line to that single type.
The first 2 arguments must be \* \* and there may be only one element
following or NULL. Systems where there would be multiple atom types
assigned to the same element are **not** supported by this pair style
due to limitations in its implementation. 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.
An example with a two component spline (new style) is TiO.meam.spline, where
the command
@ -143,6 +142,8 @@ Restrictions
This pair style requires the :doc:`newton <newton>` setting to be "on"
for pair interactions.
This pair style does not support mapping multiple atom types to the same element.
This pair style is only enabled if LAMMPS was built with the USER-MISC
package. See the :doc:`Build package <Build_package>` doc page for more
info.