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print warning when a tip4p pair style may cause incorrect results

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Axel Kohlmeyer
2021-05-19 15:33:26 -04:00
parent 32838fd4b8
commit a847a7ee9e
3 changed files with 38 additions and 0 deletions
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doc/src/pair_lj_cut_tip4p.rst
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@ -145,6 +145,22 @@ specified since a Coulombic cutoff cannot be specified for an individual I,J
type pair. All type pairs use the same global Coulombic cutoff specified in
the pair_style command.
.. warning::
Because of how these pair styles implement the coulomb interactions
by implicitly defining a fourth coordinate for the negative charge
of the TIP4P and similar water models, special care must be taken
when using these pair styles with other computations that also use
charges. Unless they are specially set up to also handle the implicit
definition of the 4th site, results are likely incorrect. Example:
:doc:`compute dipole/chunk <compute_dipole_chunk>`. For the same
reason, when using one of these pair styles with
:doc:`pair_style hybrid <pair_hybrid>`, **all** coulomb interactions
should be handled by a single sub-style with TIP4P support. All other
instances and styles will "see" the M point charges at the position
of the Oxygen atom and thus compute incorrect forces and energies.
LAMMPS will print a warning when it detects one of these issues.
----------
A version of these styles with a soft core, *lj/cut/tip4p/long/soft*\ , suitable