Add new pair styles harmonic/cut for repulsive-only harmonic interaction

[akohlmey]

Summary

This adds a pair style with a repulsive-only harmonic pairwise non-bonded potential.

Related Issue(s)

Was requested on LAMMPS MatSci forum: https://matsci.org/t/pair-style-for-harmonic-potential/40082

Author(s)

Axel Kohlmeyer, Temple U

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

New feature without modification to core code.

Implementation Notes

There is no global cutoff since the r_0 of the potential is by definition also the cutoff.

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.

[stanmoore1]

@akohlmey do you have an example for this?

[akohlmey]

@akohlmey do you have an example for this?

You can just drop it into the melt example and use pair_style harmonic/cut and pair_coeff * * 1.0 2.5