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update note for write_data command on missing coefficient data.

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Axel Kohlmeyer
2020-09-03 18:24:12 -04:00
parent ce78be864a
commit 5a7189e95f
1 changed files with 17 additions and 9 deletions
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doc/src/write_data.rst
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@ -42,16 +42,24 @@ Similar to :doc:`dump <dump>` files, the data filename can contain a "\*"
wild-card character. The "\*" is replaced with the current timestep
value.
.. note::
.. admonition:: Data in Coeff sections
The write-data command is not yet fully implemented in two
respects. First, most pair styles do not yet write their coefficient
information into the data file. This means you will need to specify
that information in your input script that reads the data file, via
the :doc:`pair_coeff <pair_coeff>` command. Second, a few of the :doc:`atom styles <atom_style>` (body, ellipsoid, line, tri) that store
auxiliary "bonus" information about aspherical particles, do not yet
write the bonus info into the data file. Both these functionalities
will be added to the write_data command later.
The write_data command may not always write all coefficient settings
to the corresponding Coeff sections of the data file. This can have
one of multiple reasons. 1) A few styles may be missing the code that
would writes those sections (if you come across one, please notify
the LAMMPS developers). 2) Some pair styles require a single pair_coeff
statement and those are not compatible with data files. 3) and finally
the default for write_data is to write a PairCoeff section, which has
only entries for atom types i == j. The remaining coefficients would
be inferred through the currently selected mixing rule. If there has
been a pair_coeff command with i != j, this setting would be lost.
LAMMPS will detect this and print a warning message unless *pair ij*
is appended to the write_data command. This will request writing a
PairIJCoeff section which has information for all pairs of atom types.
In cases where the coefficient data in the data file is incomplete,
you will need to re-specify that information in your input script
that reads the data file.
Because a data file is in text format, if you use a data file written
out by this command to restart a simulation, the initial state of the