Pair style for charge-dipole damping with Tang-Toennies function

[kateryna-goloviznina]

Summary

This is a new pair style to damp Coulomb charge-dipole interactions with the Tang-Toennies (TT) function. It allows preventing a "polarisation catastrophe" happening when strongly H-bonded systems are simulated. The pair style will be included in the USER-DRUDE package.

Related Issue(s)

Author(s)

Kateryna Goloviznina* kate.goloviznina@gmail.com, ENS de Lyon
Zheng Gong, z.gong@outlook.com, ENS de Lyon
Agilio Padua* agilio.padua@gmail.com, ENS de Lyon

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

Implementation Notes

The pair style is called coul/tt and should be used in conjunction with a main pair style including Coulomb interactions and thole pair style, or with lj/cut/thole/long equivalent to the combination of preceding two.

The coul/tt modifies the Coulomb interactions between a Drude charge (either q_D,i on a Drude particle or -q_D,i on the respective Drude core) and a charge on a non-polarizable atom, q_j. It is also possible to use this pair style to damp charge-dipole interactions between Drude cores.

The damping function was tested on several systems containing strong hydrogen bonds (solvents, ionic liquids, electrolytes) and allowed to obtain stable trajectories. The example of simulating ethylene glycol is included.

The added damping function will not affect any existing functionality.

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

Further Information, Files, and Links

Application of the Tang-Toennies function to damp electrostatic interactions in molten salts 10.1007/s00214-012-1143-9
The use of this function for strongly H-bonded systems will be described in our future paper. preprint

[akohlmey]

Please note that we are in the final stage of getting ready for a stable release, so this PR likely will have to wait until after (unless there are delays postponing the stable release and adding one more patch release).

[kateryna-goloviznina]

Thank you for the revision of my code! Yes, I understand that it will go to the winter stable version.

I still need some time to finish editing the code.

Requested changes have been implemented

[akohlmey]

@kateryna-goloviznina i have corrected the string matching issues and did a few more cosmetic changes as well as integrating the .rst file fully into the documentation build process.

[kateryna-goloviznina]

@akohlmey Thank you for your help!