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document automatic unit conversion with units and pair_coeff commands

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This commit is contained in:
Axel Kohlmeyer
2020-06-25 16:02:49 -04:00
parent c989db60a7
commit d9f07cef25
3 changed files with 20 additions and 4 deletions
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14
doc/src/pair_coeff.rst
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@ -89,14 +89,20 @@ LAMMPS so long as they are in the format LAMMPS expects, as discussed
on the individual doc pages. The first line of potential files may
contain metadata with upper case tags followed their value. These may
be parsed and used by LAMMPS. Currently supported are the "DATE:"
tag and the "UNITS:" tag. For pair styles that have been programmed
tag and the ``UNITS:`` tag. For pair styles that have been programmed
to support the metadata, the value of the "DATE:" tag is printed to
the screen and logfile so that the version of a potential file can be
later identified. The "UNITS:" tag indicates the :doc:`units <units>`
later identified. The ``UNITS:`` tag indicates the :doc:`units <units>`
setting required for this particular potential file. If the potential
file ware created for a different sets of units, LAMMPS will terminate
file was created for a different sets of units, LAMMPS will terminate
with an error. If the potential file does not contain the tag, no
check will be made.
check will be made and it is the responsibility of the user to determine
that the unit style is correct.
In some select cases and for specific combinations of unit styles,
LAMMPS is capable of automatically converting potential parameters
from a file. In those cases, a warning message signaling that an
automatic conversion has happened is printed to the screen.
When a pair_coeff command using a potential file is specified, LAMMPS
looks for the potential file in 2 places. First it looks in the

9
doc/src/units.rst
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@ -49,6 +49,15 @@ new units. And you must correctly convert all output from the new
units to the old units when comparing to the original results. That
is often not simple to do.
Potential or table files may have a ``UNITS:`` tag included in the
first line indicating the unit style those files were created for.
If the tag exists, its value will be compared to the chosen unit style
and LAMMPS will stop with an error message if there is a mismatch.
In some select cases and for specific combinations of unit styles,
LAMMPS is capable of automatically converting potential parameters
from a file. In those cases, a warning message signaling that an
automatic conversion has happened is printed to the screen.
----------
For style *lj*\ , all quantities are unitless. Without loss of