Add rebomos pair style with examples and unit test

[akohlmey]

Summary

This pull request adds pair style rebomos implementing the REBOMoS potential for MoS2 to the MANYBODY package.
This pair style had been provided outside of LAMMPS for over a decade but not updated for more recent LAMMPS versions and also had some known bugs. This version has been updated and has bugs removed and tests correctly for a variety of applications in serial and parallel and is consistent with fix numdiff.

Related Issue(s)

https://matsci.org/t/debugging-3rd-party-potential/53399

Author(s)

Original authors: James Stewart, Khanh Dang and Douglas Spearot (while at U Arkansas)
Bugfixes and updates: Axel Kohlmeyer, Temple U
Documentation: J David Schall, North Carolina Agricultural and Technical State University

Licensing

By submitting this pull request, I agree, that my contribution will be included in LAMMPS and redistributed under either the GNU General Public License version 2 (GPL v2) or the GNU Lesser General Public License version 2.1 (LGPL v2.1).

Backward Compatibility

N/A

Implementation Notes

There are small differences in forces and virial versus the original implementation due to the corrected bugs.
The bugs affected parts of the code that have only a small impact on the forces and virial, but some could trigger crashes.

Post Submission Checklist

• The feature or features in this pull request is complete
• Licensing information is complete
• Corresponding author information is complete
• The source code follows the LAMMPS formatting guidelines
• Suitable new documentation files and/or updates to the existing docs are included
• The added/updated documentation is integrated and tested with the documentation build system
• The feature has been verified to work with the conventional build system
• The feature has been verified to work with the CMake based build system
• Suitable tests have been added to the unittest tree.
• A package specific README file has been included or updated
• One or more example input decks are included

[sjplimp]

@akohlmey Do any of the spline bug fixes and neighbor list optimizations you talked about this AM, also apply to the other REBO-based pair styles?

[akohlmey]

@akohlmey Do any of the spline bug fixes and neighbor list optimizations you talked about this AM, also apply to the other REBO-based pair styles?

No. This uses the same code structure, but the details and which parameters are used are different.

Besides, this kind of issue would have resulted in unexpected NaN when running in parallel and I would have noticed the uninitialized data during previous my refactoring of AIREBO and other manybody pair styles for consistent handling of the tally functions.