Update compute_gyration_shape.cpp

[evoyiatzis]

Correct for squaring the eigenvalues of the gyration tensor and simplifying the expressions for the shape parameters

Summary

In the initial version I submitted, the eigenvalues of the gyration tensor were raised to the power of two which was erroneous. Upon fixing that logical bug, the other expressions for the shape parameters can be further simplified and made shorter.

Related Issues

Not related to any issue

Author(s)

Evangelos Voyiatzis @ Royal DSM (evoyiatzis@gmail.com)

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

No backward compatibility issues

Post Submission Checklist

Please check the fields below as they are completed after the pull request has been submitted. Delete lines that don't apply

• 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
• A package specific README file has been included or updated
• One or more example input decks are included

[athomps]

This looks good to me. Reviewing the doc page, I think it would be helpful to make two easy additions:

1. Definition of units for each of the six quantities
2. A citation to paper or textbook where these quantities are defined in more detail